Model errors in tropical cloud and precipitation revealed by the assimilation of MW imagery Katrin Lonitz, Alan Geer, Philippe Lopez + many other colleagues 20 November 2014 Katrin Lonitz ( ) Tropical precipitation 20 November 2014 1 / 20
Known (NWP) model limitations Known (NWP) model limitations when it comes to representing and assimilating precipitation Insufficient convective precipitation over land. [Geer and Baordo 2014. AMT] Underestimation of rainfall during the African monsoon over land. [Agusti-Panareda and Beljaard 2008, ECMWF Newsletter 115] Insufficient precipitation during night over land. [Lopez 2014, ECMWF Tech. Memo. 728] Convection scheme... Katrin Lonitz ( ) Tropical precipitation 20 November 2014 2 / 20
Assimilation of precipitation-related products at ECMWF What has been done? Ground-based rain radar NEXRAD (eastern half of USA), radar/gauge composite assimilation of surface rainfall product since Nov. 2011 [Lopez 2008, ECMWF Tech. Memo. 569] All-sky microwave humidity radiances 183 GHz channels on SSMIS (and MHS, early next year) assimilation of radiances since 2012 [Geer et al. 2014, ECMWF Newsletter 140] All-sky microwave imager radiances 19 90 GHz channels from SSMIS and TMI assimilation of radiances since 2009 [Bauer et al. 2010, QJRMS] Katrin Lonitz ( ) Tropical precipitation 20 November 2014 3 / 20
Assimilation of precipitation-related products at ECMWF Next few years... Ground-based rain radar OPERA, European radar network Rain gauges SYNOP stations, surface rainfall All-sky microwave humidity radiances 183 GHz channels from all sensors (e.g. ATMS humidity channels) All-sky microwave imager radiances 10 GHz channel from TMI (convective rainfall) All-sky infrared humidity radiances HIRS or IASI in 6.7 µm Space Radar EarthCARE Katrin Lonitz ( ) Tropical precipitation 20 November 2014 4 / 20
Assimilation of precipitation-related products at ECMWF Next few years... Ground-based rain radar OPERA, European radar network Rain gauges SYNOP stations, surface rainfall All-sky microwave humidity radiances 183 GHz channels from all sensors (e.g. ATMS humidity channels) All-sky microwave imager radiances 10 GHz channel from TMI (convective rainfall) All-sky infrared humidity radiances HIRS or IASI in 6.7 µm Space Radar EarthCARE Katrin Lonitz ( ) Tropical precipitation 20 November 2014 4 / 20
All-sky assimilation at ECMWF All-sky assimilation at ECMWF Obs Background/FG model Katrin Lonitz ( ) Tropical precipitation 20 November 2014 5 / 20
All-sky assimilation at ECMWF All-sky assimilation at ECMWF Background/FG model Observation Operator (RTTOV) including cloud and precipitation Obs FG O-B/ FG departures Katrin Lonitz ( ) Tropical precipitation 20 November 2014 5 / 20
All-sky assimilation at ECMWF All-sky assimilation at ECMWF Background/FG model Observation Operator (RTTOV) including cloud and precipitation Obs FG O-B/ FG departures Observation operator TL/Adjoint Moist Physics TL/Adjoint Forecast Model TL/Adjoint Control variables (winds, mass and humidity at start of assimilation window) optimized by 4DVar Katrin Lonitz ( ) Tropical precipitation 20 November 2014 5 / 20
All-sky assimilation at ECMWF All-sky assimilation at ECMWF Background/FG model Observation Operator (RTTOV) including cloud and precipitation Obs FG O-B/ FG departures Assimilation: Initial conditions for prognostic variables of forecast model Observation operator TL/Adjoint Moist Physics TL/Adjoint Forecast Model TL/Adjoint Control variables (winds, mass and humidity at start of assimilation window) optimized by 4DVar New Forecast Katrin Lonitz ( ) Tropical precipitation 20 November 2014 5 / 20
TRMM Microwave Imager (TMI) Tropical Rainfall Measuring Mission s (TRMM) Microwave Imager (TMI) http://www.eorc.jaxa.jp/trmm/about/purpose/concept j.htm dual polarized, conical scanning passive microwave radiometer semi-equatorial (+/- 35 deg) orbit: diurnal cycle 5 channels: 10 GHz - 85.5 GHz spatial resolution in 10 GHz: 72 km x 43 km Katrin Lonitz ( ) Tropical precipitation 20 November 2014 6 / 20
Points of interest Points of interest 1 Katrin Lonitz ( Location of tropical (convective) precipitation 2 Timing of precipitation: diurnal cycle 3 Intensity of precipitation ) Tropical precipitation 20 November 2014 7 / 20
Points of interest 1) (Mis)location of tropical precipitation 1) (Mis)location of tropical precipitation model resolution: 40 km x 40 km (T511) 4 August 2013 Katrin Lonitz ( ) Tropical precipitation 20 November 2014 8 / 20
2) Timing of tropical precipitation 2) Diurnal cycle over ocean - TCWV > 55 kg m 2 model resolution: 40 km x 40 km (T511) data between 30S and 30N July - August 2013 study motivated by M. Kazumori ECMWF Tech. Memo 732 Katrin Lonitz ( ) Tropical precipitation 20 November 2014 9 / 20
3) Intensity of tropical precipitation 3) Intensity of tropical precipitation model resolution: 40 km x 40 km (T511) data between 30S and 30N, August 2013 What is the impact of model resolution? How crucial is superobbing? How much does convective precipitation contribute? What is the influence of modifications in the observation operator? Katrin Lonitz ( ) Tropical precipitation 20 November 2014 10 / 20
3) Intensity of tropical precipitation 3) Intensity of tropical precipitation model resolution: 40 km x 40 km (T511) and 16 km x 16 km (T1279) data between 30S and 30N, August 2013 What is the impact of model resolution? Number of high brightness temperatures increases. Katrin Lonitz ( ) Tropical precipitation 20 November 2014 11 / 20
3) Intensity of tropical precipitation 3) Intensity of tropical precipitation model resolution: 40 km x 40 km (T511) data between 30S and 30N, August 2013 How crucial is superobbing? No superobbing of data increases number of high brightness temperatures. Katrin Lonitz ( ) Tropical precipitation 20 November 2014 12 / 20
3) Intensity of tropical precipitation 3) Intensity of tropical precipitation model resolution: 40 km x 40 km (T511) data between 30S and 30N, August 2013 How much does convective precipitation contribute? Excluding convective fluxes reduces number of high brightness temperatures. Katrin Lonitz ( ) Tropical precipitation 20 November 2014 13 / 20
3) Intensity of tropical precipitation 3) Intensity of tropical precipitation model resolution: 40 km x 40 km (T511) data between 30S and 30N, August 2013 What is the influence of modifications in the observation operator? Assuming lower fall velocities of drops increases number of high brightness temperatures. Katrin Lonitz ( ) Tropical precipitation 20 November 2014 14 / 20
Take home messages Take home messages Being aware of the limitation of model and observations is important. Spatial resolution is crucial for capturing the intensity of convective precipitation. Sensitivity studies on rainy radiances of the model show how crucial assumptions in the forward operator are. Fall speed parameterization,... More research has to be invested in the development of the observation operator in cloudy and rainy situations! We need better (and fast) radiative transfer codes! Katrin Lonitz ( ) Tropical precipitation 20 November 2014 15 / 20
Backup 2) Diurnal cycle over ocean model resolution: 40 km x 40 km (T511) data between 30S and 30N July - August 2013 study motivated by M. Kazumori ECMWF Tech. Memo 732 Katrin Lonitz ( ) Tropical precipitation 20 November 2014 16 / 20
Backup 3) Intensity of tropical precipitation model resolution: 40 km x 40 km (T511) data between 30S and 30N, August 2013 How crucial is correct data Filtering? Filtering of land contaminated point reduces slightly number of higher brightness temperatures. Katrin Lonitz ( ) Tropical precipitation 20 November 2014 17 / 20
Map of FoO [%] Backup model resolution: 40 km x 40 km (T511) data between 30S and 30N July - August 2013 gridded 2.5 x 2.5 degrees Katrin Lonitz ( ) Tropical precipitation 20 November 2014 18 / 20
Backup Map of Total Column Water Vapour [kg m 2 ] model resolution: 40 km x 40 km (T511) data between 30S and 30N 4 August 2013 Katrin Lonitz ( ) Tropical precipitation 20 November 2014 19 / 20
Backup Map of Lower troposphere stability [K] model resolution: 40 km x 40 km (T511) data between 30S and 30N 4 August 2013 Katrin Lonitz ( ) Tropical precipitation 20 November 2014 20 / 20