Synoptic Controls on Precipitation in the Valley of Oaxaca, Mexico

Dilley, Maxx

doi:10.1002/(sici)1097-0088(199609)16:9<1019::aid-joc74>3.0.co;2-q

Cited by 12 publications

(10 citation statements)

References 5 publications

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“…A bimodal regime characterizes the seasonal cycle of precipitation in southern Mexico, Central America and the Caribbean, most commonly known as midsummer drought (MSD) (Magaña et al, 1999;Gamble et al, 2008), but also as Veranillo in Central America and canícula in southern Mexico (Dilley, 1996;Amador et al, 2016;Durán-Quesada et al, 2017). The seasonal cycle in these regions is characterized by two precipitation maxima, in June and September, that are separated by a drier period in July and August.…”

Section: Introductionmentioning

confidence: 99%

The American monsoon system in HadGEM3 and UKESM1

García‐Franco

Gray

Osprey

2020

Weather Clim. Dynam.

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Abstract. The simulated climate of the American monsoon system (AMS) in the UK models HadGEM3 GC3.1 (GC3) and the Earth system model UKESM1 is assessed and compared to observations and reanalysis. We evaluate the pre-industrial control, AMIP and historical experiments of UKESM1 and two configurations of GC3: a low (1.875∘×1.25∘) and a medium (0.83∘×0.56∘) resolution. The simulations show a good representation of the seasonal cycle of temperature in monsoon regions, although the historical experiments overestimate the observed summer temperature in the Amazon, Mexico and Central America by more than 1.5 K. The seasonal cycle of rainfall and general characteristics of the North American monsoon of all the simulations agree well with observations and reanalysis, showing a notable improvement from previous versions of the HadGEM model. The models reasonably simulate the bimodal regime of precipitation in southern Mexico, Central America and the Caribbean known as the midsummer drought, although with a stronger-than-observed difference between the two peaks of precipitation and the dry period. Austral summer biases in the modelled Atlantic Intertropical Convergence Zone (ITCZ), cloud cover and regional temperature patterns are significant and influence the simulated regional rainfall in the South American monsoon. These biases lead to an overestimation of precipitation in southeastern Brazil and an underestimation of precipitation in the Amazon. The precipitation biases over the Amazon and southeastern Brazil are greatly reduced in the AMIP simulations, highlighting that the Atlantic sea surface temperatures are key for representing precipitation in the South American monsoon. El Niño–Southern Oscillation (ENSO) teleconnections, of precipitation and temperature, to the AMS are reasonably simulated by all the experiments. The precipitation responses to the positive and negative phase of ENSO in subtropical America are linear in both pre-industrial and historical experiments. Overall, the biases in UKESM1 and the low-resolution configuration of GC3 are very similar for precipitation, ITCZ and Walker circulation; i.e. the inclusion of Earth system processes appears to make no significant difference for the representation of the AMS rainfall. In contrast, the medium-resolution HadGEM3 N216 simulation outperforms the low-resolution simulations due to improved SSTs and circulation.

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Section: Introductionmentioning

confidence: 99%

The American monsoon system in HadGEM3 and UKESM1

García‐Franco

Gray

Osprey

2020

Weather Clim. Dynam.

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“…A study regarding global trends shows an increase in daily extreme precipitation in Southern Mexico over the past half century; one of the main problems in analyzing extreme climate events is the lack of high-quality, longterm climate data with adequate time resolution (Easterling et al, 2000). Most studies of extremes have focused on Northwestern and Central Mexico (e.g., Magaña et al, 2003;Cavazos et al, 2008;Arriaga-Ramírez and Cavazos, 2010;Méndez and Magaña, 2010), while only a few studies have analyzed extreme events in Southern Mexico (Dilley, 1996;Peralta-Hernández, 2009). Peralta et al (2009) in a regional study of Southern Mexico analyzed 23 extreme rainfall indices; they found an increase in extreme daily precipitation events over the 1960-2004 period, with a step-like jump in the early 1970's.…”

Section: Introductionmentioning

confidence: 99%

Variability of extreme precipitation in coastal river basins of the southern mexican Pacific region

Pérez-Morga¹,

Kretzschmar²,

Cavazos

et al. 2013

Geofísica Internacional

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Extreme wet and dry years (± 1 standard deviation, respectively), as well as the top 95 percentile (P95) of daily precipitation events, derived from tropical cyclone (TC) and nontropical cyclone (NTC) rainfall, were analyzed in coastal river basins in Southern Oaxaca, Mexico (Río Verde, Río Tehuantepec, and the Southern Coast). The study is based on daily precipitation records from 47 quality-controlled stations for the 1961 to 1990 period and TC data for the Eastern Tropical Pacific (EPAC). The aim of this study was to evaluate extreme (dry and wet) trends in the annual contribution of daily P95 precipitation events and to determine the relationship of summer precipitation with El Niño Southern Oscillation (ENSO) and the Pacifical Decadal Oscillation (PDO). A regionalization based on a rotated principal component analysis (PCA) was used to produce four precipitation regions in the coastal river basins. A significant negative correlation (significance at the 95% level) was only found with ONI in rainfall Region 3, nearest to the Gulf of Tehuantepec. Wet years, mainly linked to TC-derived P95 precipitation events, were associated with SST anomalies ≥ − °( ) 0 6 . C similar to weak La Niña and Neutral cool conditions, while dry years were associated with SST positive anomalies similar to Neutral warm conditions ≤ − °( ) 0 5 . C . The largest contribution of extreme P95 precipitation derived from TCs to the annual precipitation was observed in Region 3. A significant upward trend in the contribution of TCderived precipitation to the annual precipitation was found only in Region 1, low Río Verde.

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“…The annual cycle of precipitation in parts of southern Mexico, Central America and the Caribbean exhibits a bimodal signal characterized by two wetter periods and a drier period in between during Midsummer, most commonly referred to as Midsummer drought (MSD; Mosiño and García 1966;Magaña et al 1999;Gamble et al 2008;Perdigón-Morales et al 2018;Zhao and Zhang 2021) or locally as canícula and Veranillo (Dilley 1996). The MSD, as a relatively drier spell during the rainy season, is known to impact agriculture and crop-yield (Jobbová et al 2018;Harvey et al 2018), and recent evidence has highlighted both changes to the timing of the MSD (Anderson et al 2019) and increasingly damaging impacts of droughts to local farmers (Hellin et al 2017;Chen et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Revisiting mechanisms of the Mesoamerican Midsummer drought

et al. 2022

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Observations show that the seasonal cycle of precipitation in parts of southern Mexico and Central America exhibits a bimodal signal, known as the Midsummer drought (MSD), but there is no consensus on which processes are most relevant for the two-peak structure of the rainy season. This paper evaluates three hypotheses that could explain the MSD: the SST cloud-radiative feedback, the solar declination angle and the Caribbean Low-Level Jet (CLLJ) moisture transport hypotheses. Model experiments produced by the Met Office Hadley Centre (MOHC) for CMIP6 as well as ERA5 reanalysis data are used to critically assess the predictions of each hypothesis. The simulations capture the double peak signal of precipitation well and reasonably simulate the spatial and temporal variations of the MSD and other relevant climate features such as the CLLJ. Evidence from our analysis suggests that the Eastern Pacific SSTs do not increase in late summer in ERA5 data and only slightly increase in the simulations. More importantly, the Eastern Pacific SST variability in ERA5 and in the model experiments cannot explain the differences in the seasonality of precipitation. The net shortwave radiation at the surface shows a two-peak seasonal cycle; however, this behaviour appears to result from a strong anti-correlation of the incoming shortwave and convective activity due to cloud radiative-effects. There was no evidence found by this study of a causal link in which absorption of shortwave energy forces precipitation variations, as suggested by the solar declination angle hypothesis. The moisture convergence, CLLJ and the precipitable water vapor variations best explain the characteristics of the observed and simulated MSD, particularly for the onset of the MSD. The diagnosed variations of moisture convergence, which are synchronous with the timing of the MSD, point to a dynamic mechanism in which the low-level inflow from the Caribbean is more important for the MSD than other radiative mechanisms.

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Synoptic Controls on Precipitation in the Valley of Oaxaca, Mexico

Cited by 12 publications

References 5 publications

The American monsoon system in HadGEM3 and UKESM1

The American monsoon system in HadGEM3 and UKESM1

Variability of extreme precipitation in coastal river basins of the southern mexican Pacific region

Revisiting mechanisms of the Mesoamerican Midsummer drought

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