Dec 172016
 

Most of Mexico is above 1000 m (about 3300 ft) in elevation; as a result most of Mexico has a more temperate climate than might be expected given its latitude.

The famous explorer Alexander von Humboldt, one of the founding fathers of physical geography and meteorology, was the first to describe the vertical differentiation of climatic and vegetation zones in Mexico. Writing in 1811, he proposed the terms tierra caliente, tierra templada, and tierra fría, still widely used by non-specialists today.

Tierra caliente (hot land) includes all areas under about 900 m (3000 ft). These areas generally have a mean annual temperature above 25°C (77°F). Their natural vegetation is usually either tropical evergreen or tropical deciduous forest. Farms produce tropical crops such as sugar-cane, cacao and bananas.

Altitude zones

Altitude zones. Copyright John Wiley & Sons Inc. 2000.

Tierra templada (temperate land) is the area between 900 and 1800 m (3000 to 6000 ft) where mean annual temperatures are usually between about 18°C and 25°C (64°F to 77°F). The natural vegetation in these zones is temperate forest, such as oak and pine-oak forest. Farms grow crops such as corn (maize), beans, squash, wheat and coffee.

Tierra fria (cold land) is over 1800 m (6000 ft) where mean annual temperatures are in the range 13°–18°C (55°–64°F). At these altitudes pine and pine-fir forests are common. Farm crops include barley and potatoes. On the highest mountain tops, above the tierra fría is tierra helada, frosty land.

Even higher, and almost permanently under snow and ice, is the tierra nevada, snow-covered land.

May 122016
 

The 2016 hurricane season in Mexico for Pacific coast storms starts on 15 May and lasts until 30 November. For Atlantic storms, the hurricane season extends from 1 June to 30 November, though most hurricane activity is concentrated in the months from July to September. Hurricanes are also known as typhoons or tropical cyclones.

The table shows the World Meteorological Organization’s official list of 2016 tropical storm and hurricane names. Note that male and female names alternate. Names are often reused in future years, with the exception of the names of any particularly violent storms, which are officially “retired” from the list for a long time.

2016 Hurricane Names for the Atlantic, Gulf of Mexico and Caribbean
AlexGastonLisaRichard
BonnieHermineMatthewShary
ColinIanNicoleTobias
DanielleJuliaOttoVirginia
EarlKarlPaulaWalter
Fiona

2016 Hurricane Names for the Eastern Pacific
AgathaGeorgetteMadelineTina
BlasHowardNewtonVirgil
CeliaIvetteOrleneWinifred
DarbyJavierPaineXavier
EstelleKayRoslynYolanda
FrankLesterSeymourZeke

saffir-simpson-scale

In their early season forecast for this year, Philip Klotzbach and William Gray, researchers at Colorado State University,  expect hurricane activity in the Atlantic to be near-normal (ie close to the 30-year average). They predict that in the 2016 season 13 named storms will form in the Atlantic: 5 tropical storms, 6 moderate hurricanes (1 or 2 on the Saffir-Simpson scale), and 2 severe hurricanes (3, 4 or 5 on the Saffir-Simpson scale). These forecasts will be updated on 2 June and 31 July.

Last year’s Atlantic hurricane season was slightly below average in activity with 11 named storms: 5 tropical storms, 4 moderate hurricanes and 2 severe hurricanes. On the other hand, the 2015 Pacific hurricane season was the second most active on record, with 26 named storms, including 11 severe hurricanes.

In 2016, for the Pacific coast, Mexico’s National Meteorological Service (Servicio Metrológico Nacional, SMN) is expecting 17 named storms: 8 tropical storms, 5 moderate hurricanes (1 or 2 on the Saffir-Simpson scale), and 4 severe hurricanes (3, 4 or 5 on the Saffir-Simpson scale).

For the Atlantic coast, SMN) is expecting 13 named storms: 7 tropical storms, 4 moderate hurricanes and 2 severe hurricanes. On both coasts, these predictions indicate a slight increase in storm activity compared to long-term averages. The SNM publishes regular updates on hurricane activity (in Spanish) on its webpage and via its Twitter account: @huracanconagua.

Hurricanes and other climatological phenomena are analyzed in chapters 4 and 7 of Geo-Mexico: the geography and dynamics of modern Mexico. Buy your copy today, so you have a handy reference guide available whenever you need it.

Related posts:

Nov 232015
 

As we discussed in this earlier post, historical analysis combined with greater climatological understanding shows that many of the worst droughts and floods in Mexico have been associated with either El Niño Southern Oscillation (ENSO) events or with the related Pacific-North American Oscillation. Perhaps 65% of the variability of Mexican climate results from changes in these large-scale circulations.

The World Meteorological Organization (WMO) says the 2015-2016 ENSO is expected to be one of the three most powerful ENSO events since 1950 with effects that will last for up to eight months.

What will this winter’s El Niño bring? 

  • slightly higher ocean water temperature off west coast; some fish species may migrate northwards
  • some winter rain in north-west
  • increased winter storms, and cooler temperatures, along east coast; risk of flooding, mudslides
  • reduced summer rainfall in Mexico’s central highlands; risk of drought and lower crop yields

This winter, according to the Center for Scientific Investigation and Higher Education of Ensenada (CICESE), the Baja California Peninsula is likely to receive more rain than usual during this year’s very strong ENSO (El Niño) event.

The distribution of fish species is likely to change as the ocean temperatures are higher than usual, resulting in the migration of some species, leaving fewer fish off the coast of Baja California, one of the world’s most important commercial and sports fishing zones. Sardine fishermen may have a difficult season, incurring greater costs as they try to locate viable schools of fish.

A NASA climatologist predicts that California (USA) will be on the receiving end of more winter storms (January-March), and heavier rain, than usual. This increases the risk of hazardous mudslides in some coastal communities. It could also mean more mosquitoes, and an increased chance of contracting dengue fever or chikungunya.

What is the longer term outlook?

The first map shows likely precipitation anomalies for early next year (Spring). Areas shaded brown are areas expected to receive less rainfall than normal. Areas shaded light blue through green are predicted to get more rain than usual.

Spring precipitation anomalies

Spring precipitation anomalies in a strong El Niño year. Source: CNA

The second map shows summer precipitation anomalies. A significant reduction in rainfall is expected across most of central Mexico, though some areas in southern Mexico will likely get more rainfall than normal.

Summer precipitation anomalies in a strong El Niño year. Source: CNA

Summer precipitation anomalies in a strong El Niño year. Source: CNA

We end with one piece of good news for our more active readers. Previous El Niño events have brought great surfing to the west coast of Mexico, so make your travel and hotel plans as soon as possible.

Related posts:

Mexico has highest rate of death from lightning strikes in the Americas

 Other  Comments Off on Mexico has highest rate of death from lightning strikes in the Americas
Aug 062015
 

Last year, three Mexico City climate researchers published a comprehensive study of the 7300+ deaths due to lightning in Mexico during the period 1979 to 2011.

In “Deaths by Lightning in Mexico (1979–2011): Threat or Vulnerability?“, G. B. Raga, M. G. de la Parra and Beata Kucienska examined the distribution of fatalities due to lighting, looking for links to population density, vulnerability and other factors.

The number of deaths from lightning averaged 230 a year for the period studied. Given Mexico’s population, this means a rate of 2.72 fatalities from lightning for every million people. This is the highest rate in the Americas.

Fatalities were not distributed evenly. Seven of Mexico’s 32 states accounted for 60% of all lightning fatalities. Almost one-quarter of all deaths from lightning occurred in the State of México. Other states with high rates included Michoacán, Oaxaca and Guanajuato.

More than 45% of all deaths from lightning were young males under the age of 25 (with those aged 10 to 19 at particular risk). Overall, far fewer females died from lightning than males, though for females, too, the highest rates were for the under-25 age group.

Most deaths happened in the first half of the rainy season, between June and August, when thunderstorms are most likely.

Lightning incidence, North America, 2012-2014

Lightning incidence, North America, 2012-2014. Credit: Vaisala

What do all these numbers mean?

The incidence of lightning strikes in not equal across the country. For example, in the period 2012-2014 (see map) there were far more lightning events in in central and southern Mexico than in the northern part of the country and the Baja California Peninsula. This means that there is no clear connection between deaths by lightning and population density. However, neither is there a clear connection between deaths by lightning and the places where most lightning strikes occur.

The key factor is not just how likely a lightning strike is to occur in a particular place but also how vulnerable the local populace is. Some sectors of the population are much more vulnerable than others. Those working outdoors, for example, are at higher risk than those working indoors. This makes rural workers more vulnerable than urban workers. It also makes younger people more vulnerable than older people.

Education and awareness also play a part. Many countries have seen a dramatic fall in deaths from lightning as a direct result of launching campaigns to make people more aware and provide education about safety precautions. In the USA, fewer than 40 people now die each year from lightning, compared to about 400 in the 1930s, when the population was smaller.

For this reason, the study also concluded that the large number of deaths in Mexico is partly due to “the government’s failure to implement education and prevention strategies in communities living and working in vulnerable conditions”. Sadly, this means that there will probably be further tragic incidents similar to the one that took the lives of several members of the same family last month in the remote mountainous community of Mesa Cuata in Guanajuato.

Reference:

G. B. Raga, M. G. de la Parra, and Beata Kucienska, 2014: “Deaths by Lightning in Mexico (1979–2011): Threat or Vulnerability?”. Weather, Climate & Society, 6, 434–444.

Related posts:

Hurricane forecast and names for 2015

 Other  Comments Off on Hurricane forecast and names for 2015
Apr 202015
 

The 2015 hurricane season in Mexico for Pacific coast storms starts on 15 May and lasts until 30 November. For Atlantic storms, the hurricane season extends from 1 June to 30 November, though most hurricane activity is concentrated in the months from July to September. Hurricanes are also known as typhoons or tropical cyclones.

The table shows the World Meteorological Organization’s official list of 2015 tropical storm and hurricane names. Note that male and female names alternate. Names are often reused in future years, with the exception of the names of any particularly violent storms, which are officially “retired” from the list for a long time.

2015 Hurricane Names for the Atlantic, Gulf of Mexico and Caribbean
AnaGraceLarryRose
BillHenriMindySam
ClaudetteIdaNicholasTeresa
DannyJoaquinOdetteVictor
ErikaKatePeterWanda
Fred

2015 Hurricane Names for the Eastern Pacific
AndresGuillermoMartyTerry
BlancaHildaNoraVivian
CarlosIgnacioOlafWaldo
DoloresJimenaPatriciaXina
EnriqueKevinRickYork
FeliciaLindaSandraZelda

In their early season forecast for this year, Philip Klotzbach and William Gray, researchers at Colorado State University,  expect hurricane activity in the Atlantic to be below the 1981-2012 average. They predict that in the 2015 season 7 named storms will form in the Atlantic: 4 tropical storms, 2 moderate hurricanes (1 or 2 on the Saffir-Simpson scale), and 1 severe hurricanes (3, 4 or 5 on the Saffir-Simpson scale). These forecasts will be updated on 2 June and 31 July.

saffir-simpson-scaleAs expected, Pacific Ocean hurricanes were more common than usual in 2014, because it was an El Niño year. In 2014, there were 22 named storms (the highest total for 22 years), including a record-typing 16 hurricanes, of which 9 were major hurricanes. Hurricane activity in 2015 is also expected to be higher than the long-term average.

In 2015, for the Pacific coast, Mexico’s National Meteorological Service (Servicio Metrológico Nacional, SMN) is expecting 19 named storms: 8 tropical storms, 7 moderate hurricanes (1 or 2 on the Saffir-Simpson scale), and 4 severe hurricanes (3, 4 or 5 on the Saffir-Simpson scale). The SNM publishes regular updates on hurricane activity (in Spanish) on its webpage and via its Twitter account: @huracanconagua.

How accurate was the 2014 forecast?

The early season (May) prediction for 2014 (last year) was for 9 named storms in the Atlantic: 6 tropical storms, 2 moderate hurricanes and 1 severe hurricanes. This prediction proved to be the fairly accurate. In reality, the 2014 Atlantic season had 8 named storms: 2 tropical storms, 4 moderate hurricanes and 2 severe hurricanes

Related posts:

Monitoring air pollution in Guadalajara

 Books and resources, Teaching ideas  Comments Off on Monitoring air pollution in Guadalajara
Jun 162014
 

Air pollution in the city of Guadalajara, the state capital of Jalisco, has worsened over the past decade, though there are some recent signs of improvement :

The Jalisco Environmental Agency now has a webpage where residents and travelers alike can now monitor Guadalajara’s air quality on an hourly basis. Readings for 10 stations are superimposed on a basemap on that page, together with links to graphs showing recent trends and other meteorological data. Tabs above the map also give a link to the current wind conditions across the city. Historical data (in Spanish) can also be accessed via the link to “Datos”.

Screenshot of Guadalajara air monitoring webpage

Screenshot of Guadalajara air monitoring webpage. Note: Two stations are shown as undergoing maintenance.

The map provides summary data in IMECAs, which stands for Índice Metropolitano de la Calidad del Aire (Metropolitan Index of Air Quality). IMECAs are a compound index combining measurements of concentrations of ozone (O3), sulphur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and particles smaller than 10 micrometers (PM10).

In Guadalajara, formal smog alerts are issued if average readings rise above 150 IMECAs (“Very Bad”) for more than two consecutive hours. If readings rise above 200 IMECAs (“Extremely Bad”), then “serious alerts” impose restrictions on vehicle use and may lead to the suspension of school classes.

In Guadalajara, the worst air quality tends to be in the southern and eastern sections of the city. It also tends to occur in the months of April and May, immediately before the rainy season gets underway. The webpage system gives everyone an easy way to check these assertions!

In Guadalajara, mitigation efforts are centered mainly on reducing vehicle emissions (partly by stricter emissions testing and verification, and partly by improvements to the public transport network) since they are the main source of pollution. To date, there are no plans in Guadalajara to introduce a “Day without car” program similar to that in Mexico City:

Teaching idea

Use the Jalisco Environment Agency webpage to monitor Guadalajara’s air pollution and identify any patterns or trends related to air pollution in the city. Consider suggesting one or more hypotheses, such as “Air pollution gets worse in the afternoon”, or “The level of air pollution in eastern Guadalajara is worse than in western Guadalajara”, before testing your ideas using the online data.

Related posts:

Hurricane names and forecast for 2014

 Mexico's geography in the Press  Comments Off on Hurricane names and forecast for 2014
Apr 172014
 

The 2014 hurricane season in Mexico for Pacific coast storms starts on 15 May and lasts until 30 November. For Atlantic storms, the hurricane season extends from 1 June to 30 November, though most hurricane activity is concentrated in the months from July to September. Hurricanes are also known as typhoons or tropical cyclones.

In 2013 only two hurricanes (Manuel and Ingrid) hit Mexico, but they hit simultaneously in September, leading to more than 100 storm-related deaths and millions of dollars worth of property damage in several states, especially Guerrero.

The table shows the World Meteorological Organization’s official list of 2014 hurricane names. Note that male and female names alternate. Names are often reused in future years, with the exception of the names of any particularly violent storms, which are officially “retired” from the list for a long time.

2014 Hurricane Names for the Atlantic, Gulf of Mexico and Caribbean
ArthurGonzaloLauraRene
BerthaHannaMarcoSally
CristobalIsaiasNanaTeddy
DollyJosephineOmarVicky
EduourdKylePauletteWilfred
Fay

2014 Hurricane Names for the Eastern Pacific
AmandaGenevieveMarinaTrudy
BorisHernanNorbertVance
CristinaIselleOdileWinnie
DouglasJulioPoloXavier
ElidaKarinaRachelYolanda
FaustoLowellSimonZeke

For the Atlantic coast, Mexico’s National Meteorological Service (Servicio Metrológico Nacional, SMN) is expecting 10 named storms: 3 tropical storms, 5 moderate hurricanes (1 or 2 on the Saffir-Simpson scale), and 2 severe hurricanes (3, 4 or 5 on the Saffir-Simpson scale).

In their early season forecast for this year, Philip Klotzbach and William Gray, researchers at Colorado State University,  expect hurricane activity in the Atlantic to be significantly below the 1981-2012 average. They write that, “The tropical Atlantic has… cooled over the past several months, and the chances of a moderate to strong El Niño event this summer and fall appear to be quite high…. Historical data indicate fewer storms form in these conditions.” They predict that in the 2014 season 9 named storms will form in the Atlantic: 6 tropical storms, 2 moderate hurricanes (1 or 2 on the Saffir-Simpson scale), and 1 severe hurricanes (3, 4 or 5 on the Saffir-Simpson scale). These forecasts will be updated on 2 June and 31 July.

saffir-simpson-scalePacific Ocean hurricanes tend to be more common in El Niño years, so this year may be more active than usual. For the Pacific coast, Mexico’s National Meteorological Service (Servicio Metrológico Nacional, SMN) is expecting 15 named storms: 5 tropical storms, 7 moderate hurricanes (1 or 2 on the Saffir-Simpson scale), and 3 severe hurricanes (3, 4 or 5 on the Saffir-Simpson scale). The SNM publishes regular updates on hurricane activity (in Spanish) on its webpage and via its Twitter account: @huracanconagua.

How accurate was the 2013 forecast?

The early season (May) prediction for 2013 (last year) was for 18 named storms in the Atlantic: 9 tropical storms, 5 moderate hurricanes and 4 severe hurricanes. This prediction proved to be the least accurate forecast in recent years. In reality, the 2013 Atlantic season had 14 named storms: 1 tropical depression, 11 tropical storms, 2 moderate hurricanes and 0 severe hurricanes. Klotzbach and Gray have since looked at the possible reasons for the poor forecast and concluded that, “It appears that the primary reason was the most significant spring weakening observed since 1950 of the Atlantic thermohaline circulation.” A summary of their findings is available here.

Related posts:

Mexico’s January weather serves as a long-range forecast

 Other  Comments Off on Mexico’s January weather serves as a long-range forecast
Jan 042014
 

Many Mexicans use January’s weather to forecast what the weather will be like for the rest of the year.

Many Mexicans, especially campesinos (peasant farmers), who are closer to the land than most, believe that the weather during the month of January serves as a long-range forecast for the entire year. The precise prediction system, known as las cabañuelas, is thought to be based on long cycles of observations carried out in an age when people depended far more on the weather than they do today. The system is quite complicated.

The first twelve days of January are known as las cabañuelas “a derechas”. The weather on January 1 foretells the likely weather for the rest of the month. The weather on January 2 predicts the weather for February and so on, with the weather of January 12 suggesting likely conditions for December. The next twelve days (January 13 to 24 inclusive) are known as las cabañuelas “a rataculas”. This time, the weather of January 13 foretells December, that of January 14 November, and so on.

Jan 18: Pondering a miserable July

Next, each of the six days from January 25 to January 30 inclusive is divided at noon. The morning of January 25 represents January, the afternoon February. The morning of January 26 hints at March’s weather, while the afternoon applies to April’s, and so on.

Finally, even the 24 hours of January 31 are used. Each hour in the morning will be reflected in the weather from January to December. (Presumably the weather from midnight to 1.00am is a true reflection of what has already happened in January!) Then, each hour in the afternoon can be used to forecast future weather in the reverse direction. Hence, noon to 1.00pm gives us clues for December, 1.00 to 2.00pm for November and so on. Apparently, an alternative version, used in some parts of northern Mexico, divides January 31 into 12 periods of 2 hours each, with each division corresponding to the months in reverse order.

Whatever the details, the system is said to be at least as reliable as scientific forecasts over the same time period. (Though, thinking about it, perhaps that is not that hard!)

The same cabañuelas system is used in various parts of Spain, but the annual forecast does not always begin on the same day. For instance, in Alcozar, las cabañuelas “a derechas” begin on December 13. Elsewhere in Spain, they start on August 2 or August 13. According to Divina Aparicio de Andrés, predictions in Alcozar based on las cabañuelas lasted until well into the 1940s, but their use has declined since.

See also: The origins of the cabañuelas system of weather forecasting

This is an edited version of an article originally published on MexConnect.com

The climate of Mexico is discussed, with several maps,  in chapter 4 of Geo-Mexico: the geography and dynamics of modern Mexico. Climatic hazards, such as hurricanes, droughts and floods, are looked at in detail in chapters 4 and 7. Mexico’s cultural geography and cultural landscapes are discussed in chapter 13.

Why is northern Mexico a desert region?

 Excerpts from Geo-Mexico  Comments Off on Why is northern Mexico a desert region?
Oct 102013
 

Much of northern Mexico experiences either an arid (desert) climate (less than 250 mm [10 in] of rain/year) or a semiarid (semi-desert) climate (250–750 mm [10–30 in] of rain/year). Areas with an arid (desert) climate (see map) include most of Baja California and western Sonora (together comprising the Sonoran desert), as well as the northern section of the Central Plateau (the Chihuahuan desert). These areas can experience frost and freezing during the winter.

Major climate regions in Mexico. (Fig 4-5 of Geo-Mexico, the geography and dynamics of modern Mexico). All rights reserved.

Major climate regions in Mexico. (Fig 4-5 of Geo-Mexico, the geography and dynamics of modern Mexico). All rights reserved.

Areas of semiarid (dry steppe) climate include most of the Central Plateau as well as western sections of the Western Sierra Madre, northern Yucatán and scattered inland areas as far south as Oaxaca. The rains in this region fall mostly in the summer, and localized heavy thunderstorms are quite common. The southern parts of this climatic region are warmer than the northern parts. (Mexico’s seven climate regions)

Why do parts of northern Mexico receive very little precipitation, making them deserts?

The major reason is that the zone between the Tropic of Cancer (latitude 23.5 degrees N) and latitude 30 degrees N is influenced by the Hadley Cell. This is the name given to the atmospheric circulation in tropical regions, named after George Hadley, the English amateur meteorologist who first proposed its existence, in 1735.

The Hadley Cell

The functioning of the Hadley Cell

The Hadley Cell is the driving force behind many aspects of Mexico’s weather and climate. How does it operate? Solar heating is at a maximum near the equator and diminishes towards the poles. The area near the equator is the Intertropical Convergence Zone or ITCZ (see diagram). The heating of the ITCZ makes the air there rise, leaving an area of low pressure on the surface. This low pressure sucks in air along the earth’s surface from the subtropical high pressure areas about 30 degrees N and S of the equator creating the trade winds. The trade winds pick up moisture and latent heat over the oceans before converging from either side of the equator in the ITCZ. As the air in the ITCZ rises vertically, its water vapor condenses and rain falls from the towering convective clouds. This is the ascending limb of the Hadley cell. At a height of 10–15 km above the surface, the air, now minus its moisture, returns polewards as high level anti-trade winds. Sunbathers on Mexican beaches who notice two sets of clouds above them at different heights traveling in opposite directions are witnessing the trade winds and anti-trade winds in action.

In the subtropics, this air then descends again towards the surface to complete the cell and initiates the surface trade winds again. The descending air warms up as it sinks; its relative humidity decreases, and so no precipitation occurs; hence these high pressure subtropical areas are arid. Mexico’s arid and semiarid areas coincide with the descending air segment of the Hadley Cell and these high pressure subtropical areas.

In addition, the climate of the west coast of the Baja California Peninsula is influenced by the cool Californian current, which flows towards the south. The relative humidity of the air above it drops as the current enters warmer waters, so it is not likely to bring rain to the peninsula.

The aridity of the Sonoran desert is also partly due to its position in the rain shadow of the Western Sierra Madre. The Chihuahuan desert is in an even more marked rain shadow, protected by both the Western Sierra Madre and the Eastern Sierra Madre.

Stunning stream patterns in northern Baja California

Photographer Adriana Franco from Querétaro has taken several truly stunning artistic images of stream patterns in the semi-arid region of northern Baja California (near Mexicali). The photos, taken from an ultralight, show the details of the dendritic (= tree-like) stream patterns in this region. Dendritic stream patterns are common worldwide, but these images are exceptional. In general, dendritic stream patterns are associated with relatively gentle gradients where the underlying rocks are similar throughout the drainage basin.

Related posts

Mexico’s seven climate regions

 Excerpts from Geo-Mexico  Comments Off on Mexico’s seven climate regions
Aug 152013
 

Climatologists have developed several scientific systems to classify climates. The system developed by Wladimir Köppen in the early 20th century is one of the earliest and best known. The Köppen climate classification system assumes that climate is best reflected in native vegetation and can be accurately classified using seasonal variations in temperatures and precipitation. Mexican climatologists, including Enriqueta García, have proposed minor modifications to the Köppen system to make it more appropriate for Mexico. The following paragraphs reflect García’s revised Köppen system.

Given that Mexico has many mountains with rapid changes in elevation, temperature and rainfall, applying the Köppen system, even as modified by García, to Mexico can become extremely complicated. A relatively small area of Mexico may include several Köppen climate categories. Aggregating these areas provides a less complicated, more understandable, picture of Mexico’s climates (see map). In this scheme, Mexico has seven main climate regions, as shown on the map:

Major climate regions in Mexico. (Fig 4-5 of Geo-Mexico, the geography and dynamics of modern Mexico). All rights reserved.

Major climate regions in Mexico. (Fig 4-5 of Geo-Mexico, the geography and dynamics of modern Mexico). All rights reserved.

Two tropical climates

Mexico has two tropical climates which have average temperatures of over 18°C (64°F) for all twelve months of the year.

The first, tropical wet (Af in the Köppen system, see map), has at least 60 mm (2.4 in) of rain in every month of the year. This is the climate of the Amazon and Indonesian rainforests. In Mexico this is the climate of the Gulf Coast Plain in southern Veracruz and Tabasco (classic tierra caliente areas). It also occurs in the Oaxaca and Chiapas highlands. The rains fall all year, varying from about 120–150 mm (4–5 in) in April to 380 mm (15 in) in September.

The tropical wet-and-dry (Aw) category (see the climate graph for Cancún) has a pronounced dry season. The dry winter months typically get less than 40 mm (1 in) of rain, compared to over 150 mm (6 in) in each of the summer months. Parts of West Africa, Brazil and India have a similar climate. Much of coastal Mexico, stretching from Nayarit along the Pacific coast all the way to Guatemala, is in this category. It also covers many inland areas along the Pacific coast. Central and northern Veracruz and most of the Yucatán Peninsula also have this tropical climate with summer rains.

Climate graphs for three cities. (Fig 4.6 of Geo-Mexico,)

Climate graphs for three cities. (Fig 4.6 of Geo-Mexico, the geography and dynamics of modern Mexico) All rights reserved.

Two dry climates

Areas with an arid (desert) climate (BW) usually receive less than 250 mm (10 in) of rain a year (see climate graph for Ciudad Juárez). This is the climate of the Sahara Desert and Central Australia. In Mexico dry desert areas include most of Baja California, western Sonora, and the northern section of the Central Plateau. These areas can experience frost and freezing during the winter.

Areas with the second type of arid climate, semiarid (dry steppe) (BS), receive 250–750 mm (10–30 in) of rain a year. This is the climate of the African savanna lands and much of central Asia. In Mexico, this climate region includes most of the Central Plateau as well as western sections of the Western Sierra Madre, northern Yucatán and scattered inland areas as far south as Oaxaca. The rains in this region fall mostly in the summer, and localized heavy thunderstorms are quite common. The southern parts of this climatic region are warmer than the northern parts.

Three temperate zones

Temperate climates typically have average temperatures above 10°C (50°F) in their warmest months, and a coldest month average between 3°C and 18°C (27–64°F). Moisture characteristics distinguish between the three temperate climates.

The temperate with dry winters climate (Cw) is characterized by mild temperatures, low humidity, and summer rainfall ranging from about 600 to 1200 mm (25–45 in) per year (see climate graph for Guadalajara). This is classic tierra templada country. The low nighttime temperatures in winter are typically around 5°C (41°F). Of course, higher elevations have lower temperatures with occasional frost. The highest temperatures usually reach about 35°C (95°F), though temperatures may reach as high as 40°C (104°F). This climate is similar to that of the Kenyan Highlands. In Mexico, this climate includes parts of Nuevo León and Tamaulipas, most of the Western Sierra Madre and many mountainous areas in western, central and southern Mexico. Most of the Volcanic Axis is in this temperate with dry winters zone. Here, the major control as far as temperatures are concerned is altitude, which directly affects precise rainfall amounts and seasonality, resulting in a mosaic of microclimates and natural vegetation regions.

Compared with the temperate with dry winters climate, the humid subtropical (Cf) zone gets more rainfall, is more humid and gets rain throughout the year. The only areas of Mexico with this climate are the eastern slopes of the Eastern Sierra Madre and some parts of the southern mountain systems.

The Mediterranean climate (Cs) is the mild climate associated with Europe’s Mediterranean coast as well as the California coast. The area around Tijuana is the only part of Mexico with this type of climate. This area is relatively arid and gets less than 400 mm (15 in) of rain a year; it is unique in Mexico, being the only place that is dry in summer and gets rain only in winter.

Related posts