Abstract

In this study, twenty large-scale circulation patterns are identified to generate a synoptic classification of Weather Types (WT) over a region that comprises Mexico, the Intra-Americas Seas, Central America, and northern South America. This classification is performed using Self-Organizing Maps (SOMs) with mean sea-level pressure standardized anomalies from reanalysis. The influence of quasi-permanent pressure centers over the region, such as North Atlantic Subtropical High (NASH) and North Pacific High (NPH) are well captured. Seasonal variability of high-pressure centers for dry (November–April) and wet (May–October) periods over the entire region are also well represented in amplitude and pattern among the WTs. The NASH influence and intensification of the Caribbean low-level jet and the North American monsoon system is well captured. During the dry period, a strong trough wind advects cold air masses from mid-latitudes to the subtropics over the western Atlantic Ocean. High-frequency transitions among WTs tend to cluster around the nearest neighbors in SOM space, while low-frequency transitions occur along columns instead of rows in the SOM matrix. Low-frequency transitions are related to intraseasonal and seasonal scales. The constructed catalog can identify near-surface atmospheric circulation patterns from a unified perspective of synoptic climate variability, and it is in high agreement with previous studies for the region.

Highlights

  • Synoptic climatology investigates the connection between atmospheric circulation patterns and climatic differences [1]

  • The spatial pattern correspondence between temperature at 2 m (T2m) anomalies and the North Atlantic Subtropical High (NASH) spatial pattern in Mean Sea-Level Pressure (MSLP) is lost in the second part of the wet period from WT6 to WT10

  • We analyzed and verified a catalog of twenty Weather Types (WT). We showed this catalog to be useful in detecting key features of regional climate for MAR and adequate to describe the influence of semi-permanent centers from planetary circulation over the study region, such as the NASH and North Pacific High (NPH)

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Summary

Introduction

Synoptic climatology investigates the connection between atmospheric circulation patterns and climatic differences [1]. A methodological hallmark of synoptic climatology is data reduction, rendering a small set of physically meaningful patterns or categories from a large data volume [2] One such approach should produce a classification of spatially recognizable weather types (or weather patterns as they are sometimes named) at the daily or sub-daily time scales. Information at this temporal resolution can provide an important insight into how local or regional climates are related to atmospheric circulation processes. A very popular and widely used classification was developed by Lamb [3] to obtain a seven-WT classification of daily circulation patterns over the British Isles

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