1. Simulations of the transport of idealized short-lived tracers
to the UTLS via the Asian Summer Monsoon
Giorgio S. Taverna1, Martyn Chipperfield1, Richard Pope1, Ryan Hossaini2 and Piers Forster1
1 Institute for Climate and Atmospheric Science, University of Leeds, Leeds, UK
2 Lancaster Environment Centre, Lancaster University, Lancaster, UK
Introduction
CO50 a a a b
Recent work by many groups has focused on quantifying processes which contribute to coupling in the upper troposphere - lower stratosphere (UTLS), including transport during the Asian Summer Monsoon (ASM).
Important species which are transported include anthropogenic compounds such as CO and Very Short-Lived Substances (VSLSs). This poster investigates this transport using moderate-resolution simulations (2.8° x 2.8°) of the TOMCAT/SLIMCAT off-line 3-D chemical transport model over a 9-year timescale. The model is forced by ECMWF ERA-Interim reanalyses. a
TR5 a b
Background b
Several observations evidence the role of the Asian Monsoon in transporting chemical species from the troposphere to the stratosphere. For example :
TR50 a b
Figures 2. Maps of TOMCAT simulations of CO25, CO50, TR5 and TR50 July 1999 monthly mean at 154 hPa for simulations with ERA-interim archived updraft (a) scheme. Figures (b) shows the difference ERA-Interim archived updraft - Tiedtke convection scheme. The black box shows the ASM anticyclone region.
CO25 a
VWM
VWM b c ML ML
VSE ME
Figure 1. Horizontal structure of July-August 2005 average Microwave Limb Sounder (MLS)
(on the NASA Aura satellite) water vapour (ppmv) at 216 hPa. Thick dashed line indicates m2s-1 streamfunction contour defining the Asian monsoon anticyclone [1].
CO50 a ML ML b c
VSE
VWM
VWM ME
Methodology
Background
TR5 a ML ML
VWM b c
VWM
VSE ME
An important question for CO and VSLS is whether ASM-associated transport can take place on timescales which are short relative to their chemical lifetime.
A simulation was run which included CO25, CO50 and two artificial tracers, TR5 and TR50, with parameterized loss rates and lifetimes.
The TOMCAT Tiedtke scheme and the archived ERA-Interim updrafts have been used and the results compared.
CO25, CO50, TR50 and TR5 tracers have lifetime of 25, 50, 50 and 5 days, respectively.
CO25 and CO50 use realistic monthly and spatially varying estimates of the surface CO emissions, along with specified idealised loss rates.
TR5 and TR50 are constrained at the surface with a constant 100 ppbv mixing ratio between 32N-49N and zero at other latitudes.
TR5 has been designed to diagnose deep convective transport (timescale 1-2 days), while TR50 is typical of slower larger scale ascent (timescale 1-7 weeks) [2].
The monthly mixing ratio of these species has been averaged in the ASM anticyclone. region [20N-40N, 20E-130E ] at approx. 150 hPa [3].
3. Methodology
TR50 a
VWM b c
VSE ML ML
VWM ME
Results
Figures 3. Monthly mean TOMCAT simulations of CO25, CO50, TR5 and TR50 with ERA-Interim updraft (a), Tiedtke scheme (b) and difference ERA-Interim updraft-Tiedtke scheme (c) at 154 hPa in the ASM anticyclone.
The maps of TR5 (Figures 2a) show mixing ratio values over the ASM anticyclone for July 1999 at 154 hPa. The maxima values are consistent with accumulation specifically over the monsoon region. Figures 2b show the map difference ERA-Interim –Tiedtke scheme. The ERA-Interim updraft shows stronger transport for the realistic tracers (CO25 and CO50) and TR50 , while this is not the case for the artificial tracers TR5 and TR50.
The interannual variability of the tracers over the ASM anticyclone (Figures 3a,b) show peaks during the AM with both convection schemes. The difference ERA-Interim –Tiedtke scheme remains positive for CO25 and CO50 (Figures 3c). The artificial tracers, TR5 and TR50 show a noisy behavior, confirming the sign ambiguity shown in Figures 2b.
All the tracers do not appear to be sensitive to global climate events such as very strong and moderate El Nino years (VSE and ME), moderate La Nina (ML) and very week ASM years (VWM) [3].
Figures 4. Recent works, show that the occurrence frequency of the ASM anticyclone is very high (80%) in area 2. The mixing ratio of CO25 and CO50 averaged during the ASM seasons from , show that they don’t seem to be affected by the size of the anticyclone. seem to influence the transport .
Conclusions
The model results show peaks of the mixing ratio in the ASM anticyclone for CO25, CO50, TR5 and TR50 between in June and July in both the convective schemes.
The analysis of the data in the anticyclone and in its “core”, shows similar results in the UTLS, suggesting that the tracers distribution tends to follow the dynamical structure of the anticyclone.
Future work will focus on the transport of realistic VSLSs and climate-relevant sulfur compounds via the Asian Summer Monsoon.
Ideas or questions? a b
CO25 a a
References and acknowledgements
Ackowledgments: EU StratoClim project and University of Leeds for funding this PhD project.
References:
[1]: Park, M. et al., Transport above the Asian summer Monsoon anticyclone inferred from Aura Microwave Limb Sounder tracers. J.G.R. , 112(D16309), pp
[2]: Chen, B. et al., Climatological perspectives of air transport from atmospheric boundary layer to tropopause layer over Asian monsoon regions during boreal summer inferred from Lagrangian approach. A.C.P., 12(13), pp. 5827–5839.
[3]: Asian Monsoon historical rainfall database is available at: b b a