The Effect of the Terrain on Monsoon Convection in the Himalayan Region Socorro Medina 1, Robert Houze 1, Anil Kumar 2,3 and Dev Niyogi 3 Cloud and Precipitation Seminar, University of Washington, Seattle, 25 October University of Washington; 2 RAL, NCAR; 3 Purdue University

Precipitation distribution in relation to terrain Xie et al. (2006) Jun-Aug precipitation (mm/month) (Climatology from TRMM-PR data from ) Orography (km) Bay of Bengal Arabian Sea Pakistan Afghanistan

MOTIVATION – MONSOON 2007 (Jun-Aug) Anomaly (%) Precipitation (mm)

MONSOON CONVECTION IN THE HIMALAYAN REGION – Three part study 1Houze, Wilton, and Smull (2007) – 3D structure of intense storms and their distribution in relation to topography and surrounding oceans 2Ulrike Romatschke (Ulli) – Is extending Houze et al. (2007) study  Cloud and Precipitation Seminar Nov 15 th 3Analyze numerical simulations to investigate the detailed role of the terrain – preliminary results

MONSOON CONVECTION IN THE HIMALAYAN REGION – Three part study 1Houze, Wilton, and Smull (2007) – 3D structure of intense storms and their distribution in relation to topography and surrounding oceans 2Ulrike Romatschke (Ulli) – Is extending Houze et al. (2007) study  Cloud and Precipitation Seminar Nov 15 th 3Analyze numerical simulations to investigate the detailed role of the terrain – preliminary results

Houze, Wilton, and Smull (2007) study Data from Precipitation Radar (PR) on the Tropical Rainfall Measuring Mission (TRMM) satellite (June-September 2002/2003) Found contiguous radar echoes that exceeded some size threshold Analyzed separately convective and stratiform radar echoes

Convective and stratiform radar reflectivity echoes Horizontal cross-section Vertical cross-section convective echo Vertical cross-section stratiform echo Houze (1997)

WesternCentral Eastern Deep Intense Convective Cores 40 dBZ echo 40 dBZ echo > 10 km in height > 10 km in height Wide Intense Convective Cores 40 dBZ echo 40 dBZ echo > 1000 km 2 area > 1000 km 2 area Broad Stratiform Echo > 50,000 km 2 > 50,000 km 2 Results of Houze et al. (2007):

Example of Deep Intense Convective Core (40 dbz echo >10 km in height) Example: Reflectivity at 0900 UTC 14 Jun m winds reanalysis at 1200 UTC 14 Jun 2002 Delhi sounding 00 UTC 14 Jun 2002 Houze et al. (2007) Orography

moist dry,hot Carlson et al. 1983

Western Central Eastern Deep Intense Convective Cores 40 dBZ echo 40 dBZ echo > 10 km in height > 10 km in height Wide Intense Convective Cores 40 dBZ echo 40 dBZ echo > 1000 km 2 area > 1000 km 2 area Broad Stratiform Echo stratiform echo stratiform echo > 50,000 km 2 > 50,000 km 2 Results of Houze et al. (2007):

Example of Wide Intense Convective Core (40 dbz echo >1000 km 2 in area) Example: Reflectivity at 2208 UTC 3 Sep 2003 Houze et al. (2007)

Western Central Eastern Deep Intense Convective Cores 40 dBZ echo 40 dBZ echo > 10 km in height > 10 km in height Wide Intense Convective Cores 40 dBZ echo 40 dBZ echo > 1000 km 2 area > 1000 km 2 area Broad Stratiform Echo stratiform echo stratiform echo > 50,000 km 2 > 50,000 km 2 Results of Houze et al. (2007):

Example of Broad Stratiform Echo (>50,000 km 2 in area) Example: Infrared satellite temperature and reflectivity at ~03 UTC 11 Aug 2002 Houze et al. (2007) 10 m winds reanalysis at 00 UTC 11 Aug 2002 Tengchong sounding

MONSOON CONVECTION IN THE HIMALAYAN REGION – Three part study 1Houze, Wilton, and Smull (2007) – 3D structure of intense storms and their distribution in relation to topography and surrounding oceans 2Ulrike Romatschke (Ulli) – Is extending Houze et al. (2007) study  Cloud and Precipitation Seminar Nov 15 th 3Analyze numerical simulations to investigate the detailed role of the terrain – preliminary results

MONSOON CONVECTION IN THE HIMALAYAN REGION – Three part study 1Houze, Wilton, and Smull (2007) – 3D structure of intense storms and their distribution in relation to topography and surrounding oceans 2Ulrike Romatschke (Ulli) – Is extending Houze et al. (2007) study  Cloud and Precipitation Seminar Nov 15 th 3Analyze numerical simulations to investigate the detailed role of the terrain – preliminary results

OBJECTIVES Evaluate if high-resolution models can predict the structures observed by Houze et al. (2007) Test the ideas put forward in that study: –Investigate why the intense convection is often observed over the foothills –Analyze the relative roles of orography and synoptics in systems observed in association with Bay of Bengal depressions

NUMERICAL SIMULATIONS Weather Research and Forecasting (WRF v2.1.1) model (runs conducted by Anil Kumar, NCAR/Purdue University) –NCEP Reanalysis used as initial and boundary conditions (6 hourly) –Bulk microphysical parameterization: WRF Single-Moment with 6 water substances Isolated deep convective system: dx 1 =9 km; dx 2 = 3 km (14 Jun 2002)  Simulation couldn’t capture system Wide intense convective system (3 Sep 2003) Broad stratiform system (11 Aug 2002) HYSPLIT model trajectories using NCEP reanalysis (

Wide convective system simulation Time: UTC 3 Sep 2003 ( LST) Terrain and accumulated precipitation (mm) Domain 1: dx = 9 kmDomain 2: dx = 3 km Pakistan India

Wide convective system Evaluation at 2130 UTC 03 Sep 2003 (0400 LST, t=3.5 h) Observations Infrared satellite temperature (shaded, K) and low-resolution terrain (black contours, km) WRF-simulation Cloud top temperature (shaded, K) and terrain (black contours, m) PakistanIndiaPakistanIndia

Wide convective system Evaluation at 2130 UTC 03 Sep 2003 (0400 LST, t=3.5 h) Observations Infrared satellite temperature (shaded, K) and low-resolution terrain (black contours, km) WRF-simulation Cloud top temperature (shaded, K) and terrain (black contours, m) PakistanIndiaPakistanIndia

Wide convective system Evaluation at 2230 UTC 03 Sep 2003 (0500 LST, t=4.5 h) Observations Infrared satellite temperature (shaded, K) and low-resolution terrain (black contours, km) WRF-simulation Cloud top temperature (shaded, K) and terrain (black contours, m) PakistanIndiaPakistanIndia

Wide convective system Evaluation at 2300 UTC 03 Sep 2003 (0530 LST, t=5.0 h) Observations Infrared satellite temperature (shaded, K) and low-resolution terrain (black contours, km) WRF-simulation Cloud top temperature (shaded, K) and terrain (black contours, m) PakistanIndiaPakistanIndia

Wide convective system – Evaluation of reflectivity (22 UTC 3 Sep) Observations WRF-simulation

Wide convective system – Hypotheses testing HYPOTHESIS - Low-level moist southwesterly flow was capped by dry air flowing off the high Tibetan Plateau or the Afghan mountains Surface water vapor mixing ratio (g/kg) and windsBackward trajectories (HYSPLIT/NCEP) km 2.5 km

Wide convective system – Hypotheses testing HYPOTHESIS - Low-level moist southwesterly flow was capped by dry air flowing off the Afghan mountains Surface dew point depression (°C)

Wide convective system – Hypotheses testing HYPOTHESIS - Low-level moist southwesterly flow was capped by dry air flowing off the Afghan mountains Soundings at 1800 UTC Dry side Moist side

Wide convective system – Hypotheses testing HYPOTHESIS - Convection started where the potentially unstable column was subjected to orographic lifting CAPE (J/kg)

Wide convective system – Hypotheses testing HYPOTHESIS - Convection started where the potentially unstable column was subjected to orographic lifting Surface dew point depression (°C) and vertically integrated mixing ratio of precipitating hydrometeors (mm) at 1925 UTC (t=1.25 h)

Wide convective system – Hypotheses testing HYPOTHESIS - Convection started where the potentially unstable column was subjected to orographic lifting Mixing ratio (g/kg) of water vapor (shaded), cloud hydrometeors (dark red) and precipitating hydrometeors (dark blue) at 1815 UTC

Wide convective system – Hypotheses testing HYPOTHESIS - Convection started where the potentially unstable column was subjected to orographic lifting Mixing ratio (g/kg) of water vapor (shaded), cloud hydrometeors (dark red) and precipitating hydrometeors (dark blue) at 1830 UTC

Wide convective system – Hypotheses testing HYPOTHESIS - Convection started where the potentially unstable column was subjected to orographic lifting Mixing ratio (g/kg) of water vapor (shaded), cloud hydrometeors (dark red) and precipitating hydrometeors (dark blue) at 1845 UTC

Wide convective system – Hypotheses testing HYPOTHESIS - Convection started where the potentially unstable column was subjected to orographic lifting Mixing ratio (g/kg) of water vapor (shaded), cloud hydrometeors (dark red) and precipitating hydrometeors (dark blue) at 1900 UTC

Wide convective system – Role of the NW concave indentation of the terrain Dew point depression > 10°C CIN > 150 J/kg Temperature > 31°C ‘Idealized’ (highly smoothed) low-level variables CAPE > 1800 J/kgMixing ratio > 20 g/kg Relative Humidity (% ) - Shaded

CONCLUSIONS Convective systems High-resolution model was able to predict the observed structures (if the system is wide enough AND the model has enough resolution) In Wide Intense Convective storm, the terrain appears to play three main roles: –The NW concave indentation of the terrain increases the existing humidity gradients –Elevated layer of dry, warm air originates over the Afghan mountains and caps the moist low-level flow  allows buoyancy to build up –The convection is triggered at the small features of terrain (h<0.5 km): orographic lifting, convergence or both

Broad stratiform system simulation Time: 12 UTC 10 Aug – 03 UTC 11 Aug 2003 ( LST) Terrain and accumulated precipitation (mm) Domain 1: dx = 27 kmDomain 2: dx = 9 km

Broad stratiform system – Evaluation of low-levels winds at 00 UTC 11 Aug 2002 Observations 10 m winds and wind speed (m/s) WRF-simulation Surface winds and wind speed (m/s) and terrain (red contours)

Broad stratiform system – Evaluation of IR temperature and reflectivity Observations WRF-simulation

Broad stratiform system – Sounding at Tengchong at 00 UTC 11 Aug 2002 ObservationsWRF-simulation

Broad stratiform system – Role of the Bay of Bengal Depression ‘Idealized’ (highly smoothed) low-level variables Rainrate > 5 mm/hrWind speed > 5m/s Mixing ratio > 21 g/kg LOW SLP

PRELIMINARY CONCLUSIONS – Broad stratiform system The high-resolution model was able to predict the observed structures The Bay of Bengal depression provides low- level moisture and cross-barrier flow Low-level flow channeled between individual ranges and impinges into the NE indentation of the Himalayas

Concluding remark…. Schultz et al “In diagnosing precipitation processes, assessing the mechanism for forcing ascent should be the primary concern. The degree of instability… merely modulates the response to the forcing”

Wide convective system – Role of the NW concave indentation of the terrain Dew point depression > 10°C CIN > 150 J/kg Temperature > 31°C ‘Idealized’ (highly smoothed) low-level variables CAPE > 1800 J/kgMixing ratio > 20 g/kgEquivalent potential temperature > 364 K

Wide convective system – Hypotheses testing HYPOTHESIS - Convection started where the potentially unstable column was subjected to orographic lifting CAPE (for parcel with max theta_e, J/kg)CIN (for parcel with max theta_e, J/kg)

Wide convective system Evaluation at 1830 UTC 03 Sep 2003 Observations Infrared satellite temperature (shaded, K) and low-resolution terrain (black contours, km) WRF-simulation Cloud top temperature (shaded, K) and terrain (black contours, m) PakistanIndiaPakistanIndia

Wide convective system Evaluation at 1900 UTC 03 Sep 2003 Observations Infrared satellite temperature (shaded, K) and low-resolution terrain (black contours, km) WRF-simulation Cloud top temperature (shaded, K) and terrain (black contours, m) PakistanIndiaPakistanIndia

Wide convective system Evaluation at 2100 UTC 03 Sep 2003 (XXX LST, t=X h) Observations Infrared satellite temperature (shaded, K) and low-resolution terrain (black contours, km) WRF-simulation Cloud top temperature (shaded, K) and terrain (black contours, m) PakistanIndiaPakistanIndia

Broad stratiform system simulation Terrain and accumulated precipitation (mm)

Broad stratiform system – Hypotheses testing HYPOTHESIS – The flow over the terrain enhances the mesoscale precipitation areas Vertically integrated precipitating mixing ratio over 15 h (mm)

Broad stratiform system – Hypotheses testing HYPOTHESIS – The flow over the terrain enhances the mesoscale precipitation areas Cloud water mixing ratio and vertical velocity

Stratiform case

Broad stratiform system – Evaluation of 200 mb winds at 00 UTC 11 Aug 2002 Observations wind speed (m/s) WRF-simulation wind speed (m/s) and terrain (red contours)

Wide convective system – Hypotheses testing HYPOTHESIS - Convection started where the potentially unstable column was subjected to orographic lifting Mixing ratio (g/kg) of water vapor (shaded), cloud hydrometeors (dark red) and precipitating hydrometeors (dark blue) at 1800 UTC