Impact of land convection on the water vapor and temperature variability in the TTL with an emphasis over Bauru (Brazil)
Abstract
A highly debated issue in the troposphere-to-stratosphere transport and processes controlling the water vapor (H2O) balance in the stratosphere is the role of deep overshooting over intense convective regions and interplay between hydration and dehydration processes in the Tropical Tropopause Layer (TTL). TRO-Pico is a 5-year project aiming to monitor the H2O amount during the wet season. The project relies on field campaigns held in Bauru (22.3°S; 49.1°W), Brazil, and involves a combination of balloon-borne measurements, ground-based and space-borne observations and modeling. More specifically, the study inter-compares over different time and spatial scales, the Vaisala RS-92GDP radiosondes, the Pico-SDLA and the Flash-B hygrometers datasets from the 2012 TRO-Pico campaign with the Aura-MLS limb sounder, the MetOp-IASI and the Aqua-AIRS nadir sounders, the Chemistry-Climate Model CNRM-CCM and the ECMWF analysis datasets. At the tropical scale, H2O evolution is influenced by two distinct regimes: 1) a tropospheric regime characterized by a vertical propagation, and strong negative (weakly positive) day-night variations in (non-) convective periods over land, and 2) a stratospheric regime with a propagation impacted by the 'Tape Recorder Effect' and small day-night variations, with a differentiation occurring approximately at the 360-K level of potential temperature. The temperature is subject to positive day-night variations over land increasing (decreasing) as the pressure decreases, with maximum amplitude above the Cold Point (CP) around 80 hPa in (non-) convective periods. At the local scale over Bauru, in convective periods, the shape of the diurnal cycle of H2O draws an early afternoon minimum in the Upper Troposphere (UT), consistent with the late afternoon maximum of convection. The diurnal cycle of temperature has a late morning minimum in the UT, shifted to the night at the CP level, also consistent with the injection of cold air by deep convection. Regarding the different H2O datasets, between 100 and 50 hPa we obtained a good consistency (within 10%) between MLS and the hygrometers while IASI overestimates from 2 to 3.5 ppmv (50-180%) the H2O content. The temperature is well depicted by IASI with respect to the hygrometers (within 3 K at the CP and less in the UT) but MLS measures a 4-K colder CP than IASI.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A31A0003C
- Keywords:
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- 3362 ATMOSPHERIC PROCESSES / Stratosphere/troposphere interactions