Abstract

Abstract. The contribution of deep convection to the amount of water vapour and ice in the tropical tropopause layer (TTL) from the tropical upper troposphere (UT; around 146 hPa) to the tropopause level (TL; around 100 hPa) is investigated. Ice water content (IWC) and water vapour (WV) measured in the UT and the TL by the Microwave Limb Sounder (MLS; Version 4.2) are compared to the precipitation (Prec) measured by the Tropical Rainfall Measurement Mission (TRMM; Version 007). The two datasets, gridded within 2∘ × 2∘ horizontal bins, have been analysed during the austral convective season, December, January, and February (DJF), from 2004 to 2017. MLS observations are performed at 01:30 and 13:30 local solar time, whilst the Prec dataset is constructed with a time resolution of 1 h. The new contribution of this study is to provide a much more detailed picture of the diurnal variation of ice than is provided by the very limited (two per day) MLS observations. Firstly, we show that IWC represents 70 % and 50 % of the total water in the tropical UT and TL, respectively, and that Prec is spatially highly correlated with IWC in the UT (Pearson's linear coefficient R=0.7). We propose a method that uses Prec as a proxy for deep convection bringing ice up to the UT and TL during the growing stage of convection, in order to estimate the amount of ice injected into the UT and the TL, respectively. We validate the method using ice measurements from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) during the period DJF 2009–2010. Next, the diurnal cycle of injection of IWC into the UT and the TL by deep convection is calculated by the difference between the maximum and the minimum in the estimated diurnal cycle of IWC in these layers and over selected convective zones. Six tropical highly convective zones have been chosen: South America, South Africa, Pacific Ocean, Indian Ocean, and the Maritime Continent region, split into land (MariCont-L) and ocean (MariCont-O). IWC injection is found to be 2.73 and 0.41 mg m−3 over tropical land in the UT and TL, respectively, and 0.60 and 0.13 mg m−3 over tropical ocean in the UT and TL, respectively. The MariCont-L region has the greatest ice injection in both the UT and TL (3.34 and 0.42–0.56 mg m−3, respectively). The MariCont-O region has less ice injection than MariCont-L (0.91 mg m−3 in the UT and 0.16–0.34 mg m−3 in TL) but has the highest diurnal minimum value of IWC in the TL (0.34–0.37 mg m−3) among all oceanic zones.

Highlights

  • Water vapour (WV) is one of the main greenhouse gases and has an important impact on the climate, in the tropics

  • The anomalies of the diurnal cycle of ice water content (IWC) measured by SubmillimeterWave Limb-Emission Sounder (SMILES) near the tropopause level (TL), the diurnal cycle of partial ice water path (pIWP) in the troposphere, and the diurnal cycle of Prec measured during the convective period of December 2009 to February 2010 are presented in Fig. 11a over the three land study zones and in Fig. 11b over the three ocean study zones, both with a running average of 6 h. ton, toUnT, and toTnL are the times of the minimum of Prec (Precmin), pIWP, and IWC (IWCmin), respectively

  • To quantify the amount of ice injected into the tropical upper troposphere (UT) and the tropopause layer (TL) and the processes linked to the ice diurnal variation, it is important to better understand the amount of total water in these layers and the amount of water entering into the lower stratosphere (LS)

Read more

Summary

Introduction

Water vapour (WV) is one of the main greenhouse gases and has an important impact on the climate, in the tropics. WV concentrations are limited by temperature, which regulates the saturation mixing ratio in air masses (Hartmann et al, 2001; Fueglistaler et al, 2009; Khaykin et al, 2013). WV is much smaller in the upper troposphere (UT) and stratosphere than in the lower troposphere. Despite the small concentrations, the WV distribution in the tropical upper troposphere Soden et al, 2008) and stratosphere Solomon et al, 2010) plays an important role in climate, including the determination of the overall radiative balance of the troposphere. Dion et al.: Ice injected into the tropopause by deep convection

Objectives
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call