AMMA-UK WP3 – Convection and dynamics Doug Parker Institute for Atmospheric Science School of Earth and Environment University of Leeds 29 November 2004

WP3 Objectives To explain the basic dynamics and transport properties of the WAM system, including the diurnal cycle of the boundary layer control on the monsoon, and the response to shallow and deep cumulus convection.

Water vapour 17/6/97 Moist convection in the south, dry convection in the north (the Sahara): a ‘natural laboratory’ for tropical continental convection. Monsoon winds African Easterly Jet (AEJ) 600 hPa

Shallow cumulus Mixed layer Deep convection

1. The analysis of the African Easterly Jet is good ECMWF analyses (Adrian Tompkins; in Thorncroft et al, BAMS 2003): SaharaITCZ

Courtesy Tompkins, ECMWF. 700 hPa zonal winds, averaged over August 2003 Systematic error! We need to represent the physics better. 2. The forecast has systematic error

3. Significnt errors in ECMWF PBL fields compared to observations (Aida Diongue; in Thorncroft et al., BAMS 03) Potential temperature Equivalent potential temperature

There is cool, humid air too far north. Surface fluxes? Advective fluxes? Column radiation?

4. The monsoon flow is active at night and in the morning.

The observed monsoon (v-wind) is much more irregular. Recent rainfall

Chris Taylor, CEH Wallingford Surface temperature (1200 UTC) and boundary layer TKE in the afternoon (around 1500 UTC)

WAM dynamics  By day, the boundary layer ‘maps’ onto soil moisture  By night, airflow responds to pressure gradients

WP3 Objectives Convection-soil moisture-diurnal  WP3.1 To develop validated model case studies of the diurnal cycle of convection in the continental WAM, and over anomalies of soil moisture (with WP1; using OWP1, OWP3 and OWP4 data).  WP3.2 To use case studies to quantify the response of the WAM dynamics to Mesoscale Convective Systems (MCSs) (using OWP1,3,4).

Mixing ratio – an atmospheric tracer showing nocturnal circulations

WP3 Objectives: Transport  WP3.3 To quantify the transport properties of dry and moist convective circulations, on the mesoscale and the continental scale, through model case studies and through use of chemical tracers that act as markers of source regions and of air mass ages (with WP4). Within this, to model mixing in the monsoon layer and its implication for the monsoon fluxes (using OWP1,3,4 data).

C. M. Taylor et al, QJRMS, 2005

WP3 Objectives: synoptic  WP3.4 To develop synoptic cases studies of AEW structure both north and south of the AEJ, and explore the interaction of these AEWs with soil moisture patterns (with WP1; using OWP1,3,4 data).  WP3.5 To describe the evolution of the SAL on synoptic and diurnal timescales.

Flight patterns  Stacked N-S legs in association with MCSs  Early morning / late evening  Long straight legs in boundary layer

Summary of ‘soundbites’ 1.The analysis of the African Easterly Jet is good 2.The forecast has systematic error 3.Significnt errors in ECMWF PBL fields compared to observations 4.The monsoon flow is active at night and in the morning

African Monsoon Multidisciplinary Analyses Afrikanske Monsun: Multidisiplinære Analyser Afrikaanse Moesson Multidisciplinaire Analyse Analisi Multidisciplinare per il Monsone Africano Afrikanischer Monsun: Multidisziplinäre Analysen  Analisis Multidiciplinar de los Monzones Africanos  Analyses Multidisciplinaires de la Mousson Africaine