1. An investigation of tropical wave activity and its interaction with deep convection based on ISCCP products Ademe Mekonnen 1 and William B. Rossow 2 1) EES, North Carolina A&T State University 2) CREST Institute, The City College of New York ISCCP at 30: What Do We Know and What Do We Still Need to Know? CREST at City College, New York, NY 22-25 April 2013 4/24/131

2. Goals: Understand the process of convectively active events, transitions (WS perspective) Investigate the role of deep convection on wave initiation Investigate the interaction between deep convection and tropical easterly waves  effects of waves on convection: quantitative description? 4/24/132

3. 3 Area of interest Elevation map 4/24/13 Current work: AEWs and deep convection

4. 4 Data and methods Data - Weather state (WS) data from ISCCP D1 - Wind from ECMWF reanalysis - CS/CT data WS: 2.5 o, 3-hrly ERA-Interim: 1.5 o, 6-hrly, 37-pressure levels period of record: 1983-2005 Methods - time-filtering, space-time filtering (WK99) - regression analysis as in Wheeler et al (2000) 4/24/13

5. 5 The WS data: Identified objectively by distinctive patterns in a joint frequency distributions of cloud top pressure and cloud optical thickness values using a K-means cluster analysis method (Rossow et al 2005; Jakob and Tselioudis 2003; Rossow and Schiffer 1991, 1999). 4/24/13

6. 6 Cloud top pressure vs. optical thickness patterns of Weather States (07/1983-12/2004; 35S-35N). 4/24/13

7. 7 Weather states (JAS 1984-2004) WS1 WS2 WS3 WS4 4/24/13

8. some Results 4/24/138

9. 9 Lag (days) WS1, V’ WS3, V’ WS RFO and 700V' based on 2-10 day filtered 700hPa V’ at 12.5N, 30E. (WS shaded and V’ contoured; 0.3ms -1 ). The cross-sections are for 7.5-12.5N. JAS 4/24/13

10. 10 Lag (days) 4/24/13 WS1 shaded WS3 contoured *Only positive anomalies are shown

11. 4/24/1311 Daily frequency of occurrences of WS and 200-hPa Divergence regressed onto 2-10- day filtered 700-v at 12.5N, 30E. WS anomalies (shaded), divergence (contoured) WS1, 200DWS3, 200D

12. Daily frequency of occurrences of WS and 200-hPa wind regressed onto 2-10-day filtered 200-v at 12.5N, 30E. WS anomalies (shaded), wind (contoured) 4/24/1312

13. 13 Questions : Mechanisms for WS transition o WS3 leading to WS1 and then easterly waves develop downstream? or o WS3 leading to easterly wave genesis and waves organize WS1 ? AEW phase variation vs. WS The role of mountains & diurnal cycle 4/24/13

14. 14 Magnitude of wind shear (m/s; JAS 1984-2005)

15. Mean shear (200-850-hPa) Daily frequency of occurrences of WS1 and wind shear regressed onto 2-10-day filtered 700-v at 12.5N, 30E. WS1 anomalies (shaded), wind shear (contoured) 4/24/1315

16. Daily frequency of occurrences of WS3 and wind shear regressed onto 2-10-day filtered 700-v at 12.5N, 30E. WS3 anomalies (shaded), wind shear (contoured) 4/24/1316 Mean shear (200-850-hPa)

17. 4/24/1317 Thanks. Questions? Comments?