Ice injected into the tropopause by deep convection - Part 2: Over the Maritime Continent.

Citation metadata

From: Atmospheric Chemistry and Physics(Vol. 21, Issue 3)
Publisher: Copernicus GmbH
Document Type: Article
Length: 509 words

Document controls

Main content

Abstract :

The amount of ice injected into the tropical tropopause layer has a strong radiative impact on climate. A companion paper (Part 1) used the amplitude of the diurnal cycle of ice water content (IWC) as an estimate of ice injection by deep convection, showed that the Maritime Continent (MariCont) region provides the largest injection to the upper troposphere (UT; 146 hPa) and to the tropopause level (TL; 100 hPa). This study focuses on the MariCont region and extends that approach to assess the processes, the areas and the diurnal amount and duration of ice injected over islands and over seas during the austral convective season. The model presented in the companion paper is again used to estimate the amount of ice injected (ÎIWC) by combining ice water content (IWC) measured twice a day by the Microwave Limb Sounder (MLS; Version 4.2) from 2004 to 2017 and precipitation (Prec) measurements from the Tropical Rainfall Measurement Mission (TRMM; Version 007) binned at high temporal resolution (1 h). The horizontal distribution of ÎIWC estimated from Prec (ÎIWC.sup.Prec) is presented at 2"x2" horizontal resolution over the MariCont. ÎIWC is also evaluated by using the number of lightning events (Flash) from the TRMM-LIS instrument (Lightning Imaging Sensor, from 2004 to 2015 at 1 h and 0.25.sup." x 0.25.sup." resolution). ÎIWC.sup.Prec and ÎIWC estimated from Flash (ÎIWC.sup.Flash) are compared to ÎIWC estimated from the ERA5 reanalyses (ÎIWC.sup.ERA5) with the vertical resolution degraded to that of MLS observations (ÎIWC.sup.ERA5). Our study shows that the diurnal cycles of Prec and Flash are consistent with each other in phase over land but different over offshore and coastal areas of the MariCont. The observational ÎIWC range between ÎIWC.sup.Prec and ÎIWC.sup.Flash, interpreted as the uncertainty of our model in estimating the amount of ice injected, is smaller over land (where ÎIWC.sup.Prec and ÎIWC.sup.Flash agree to within 22 %) than over ocean (where differences are up to 71 %) in the UT and TL. The impact of the MLS vertical resolution on the estimation of ÎIWC is greater in the TL (difference between ÎIWC.sup.ERA5 and â©ÎIWC.sup.ERA5 ⪠of 32 % to 139 %, depending on the study zone) than in the UT (difference of 9 % to 33 %). Considering all the methods, in the UT, estimates of ÎIWC span 4.2 to 10.0 mg m.sup.-3 over land and 0.4 to 4.4 mg m.sup.-3 over sea, and in the TL estimates of ÎIWC span 0.5 to 3.9 mg m.sup.-3 over land and 0.1 to 0.7 mg m.sup.-3 over sea. Finally, based on IWC from MLS and ERA5, Prec and Flash, this study highlights that (1) at both levels, ÎIWC estimated over land can be more than twice that estimated over sea and (2) small islands with high topography present the largest ÎIWC (e.g., island of Java).

Source Citation

Source Citation   

Gale Document Number: GALE|A651885414