Translating weather scale isotopic composition of rainfall to convective activity over Costa Rica
Abstract
The contrast between the spatial scale of Costa Rica and that of convective systems limits the interpretation of the impact convective activity has on the spatial distribution of rainfall. Rainfall isotopic composition offers a unique independent diagnosis to assess the convective nature of the rain producing systems and how it maps onto rainfall. From 5 August - 9 October 2019 as part of the Organization of Tropical East Pacific Convection (OTREC) field campaign, a surface network consisting of 16 sites nominally recording temperature, relative humidity, pressure, wind speed, wind direction, rain, and solar radiation, with a subset of ten sites providing total column water vapor, was deployed across Costa Rica. In addition, rainfall samples for isotopic analysis were collected at four key sites in a transect from the Caribbean to the Central Valley. The purpose of this study is to use the OTREC observations to better understand the characteristics of convection over the geographically diverse terrain of Costa Rica and link it to the synoptic activity. Outgoing longwave radiation, cloud top temperature and precipitation are used together with rainfall stable isotopes to classify the stage of the convection as isolated deep cores or stratiform in nature. A key finding of this study is that the characteristics convection over Costa Rica (land/ocean and convective/stratiform) are significantly impacted by the passage of easterly waves over the region. According to the results, the westward propagation of easterly waves is recorded in the sub-daily isotopic composition of rainfall across the transect and the waves passage in the convective phase dominates the isotopic composition of daily samples. Based on this result, the analysis of the impact of easterly waves over rainfall and its isotopic composition in the Central Valley is extended for the 2019-2020 period using daily rainfall samples. The results show how the isotopic signature becomes a feature of convective rainfall during the second leg of the rainy season in contrast with the first leg of the rainy season for which the local scale is dominant. The goal of this detailed observational analysis is to leverage a new re-interpretation of isotopic archives in the tropics to better understand the role easterly waves have on the activation of convection over complex terrain.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA099...05D
- Keywords:
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- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3310 Clouds and cloud feedbacks;
- ATMOSPHERIC PROCESSES;
- 3314 Convective processes;
- ATMOSPHERIC PROCESSES;
- 3371 Tropical convection;
- ATMOSPHERIC PROCESSES