The 13 years of TRMM Lightning Imaging Sensor:

Transcription

1 The 13 years of TRMM Lightning Imaging Sensor: From individual flash characteristics to decadal tendencies R. I. Albrecht1,2, S. J. Goodman3, W. A. Petersen4, D. E. Buechler5, E. C. Bruning6, R. J. Blakeslee4, H. J. Christian5 1 Instituto Nacional de Pesquisas Espaciais (INPE/CPTEC) Cooperative Institute for Climate and Satellites (CICS/UMD) 3 National Oceanic and Atmospheric Administration (NOAA/NESDIS/GSFC) 4 NASA Marshall Space Flight Center (NASA/MSFC) 5 University of Alabama Huntsville (UAH) 6 Texas Tech University (TTU) 2

2 Introduction The Tropical Rainfall Measuring Mission (TRMM) satellite was launch in November The TRMM Lightning Imaging Sensor (LIS) is a CCD array that detects lightning events at ~4.3 km of resolution during 92 seconds at nadir: This short sampling time during the satellite overpass requires several years to compute high resolution climatology. Nowadays, LIS has collected lightning measurements for over 13 years which enable us: To make compilation of a total lightning climatology maps in high resolution such as 0.25o and 0.10o of horizontal resolution. To infer total lightning trends over the last decade.

3 Methodology Each LIS orbit was tracked over the surface of the Tropics (±35 o of latitude): in 0.50o, 0.25o and 0.10o grids computing the view time and the number of flashes at each pixel during each orbit passage. flash count at each pixel was corrected by the instrument flash detection efficiency according to the pixel s local standard time (LST) [Boccippio et al., 2002]

4 Methodology Flash rate density (FRD fl km-2 yr-1) was calculated for the 13 year and here we analyze: 1) The climatological total lightning map and its maximums 2) Individual flash characteristics in respect to precipitation type 3) Decadal trends

5 Results 1) The climatological total lightning map and its maximums

6 Results 1) The climatological total lightning map and its maximums fl km-2 yr-1 Christian et al. [2003] LIS+OTD 0.50o, LIS 0.25o, LIS 0.10o,

7 1) The climatological total lightning map and its maximums 1st maximum in Christian et al. [2003] (0.50o resolution): -2-1 Kamembe, Rwanda: 82.7 fl km yr, with 221 thunderstorm days per year. 1st maximum in LIS 0.25o and 0.10o ( ): fl km-2 yr Lake Maracaibo, Venezuela: 250 fl km yr, with 333 thunderstorm days per year

8 1) The climatological total lightning map and its maximums fl km-2 yr-1 Nocturnal maximum due to a convergence of breezes over a warm lake: Minimum mean lake water temperature of 28.7oC Mountain-valley breeze Lake breeze Sea breeze Easterlies

9 1) The climatological total lightning map and its maximums fl km-2 yr-1 Nocturnal maximum due to a convergence of breezes over a warm lake: Minimum mean lake water temperature of 28.7oC Mountain-valley breeze Lake breeze Sea breeze Easterlies

10 1) The climatological total lightning map and its maximums fl km-2 yr-1 Nocturnal maximum due to a convergence of breezes over a warm lake: Minimum mean lake water temperature of 28.7oC Mountain-valley breeze Lake breeze Sea breeze Easterlies

11 1) The climatological total lightning map and its maximums fl km-2 yr-1 Nocturnal maximum due to a convergence of breezes over a warm lake: Minimum mean lake water temperature of 28.7oC Mountain-valley breeze Lake breeze Sea breeze Easterlies

12 1) The climatological total lightning map and its maximums fl km-2 yr-1 Nocturnal maximum due to a convergence of breezes over a warm lake: Minimum mean lake water temperature of 28.7oC Mountain-valley breeze Lake breeze Sea breeze Easterlies

13 Results 2) Individual flash characteristics in respect to precipitation type (please see the proceedings for details)

14 Results 3) Decadal trends

15 Results 3) Decadal trends: Flashes from LIS orbit dataset at 0.5o resolution: Post-boost orbits field of view were corrected by the preboost swath and LIS detection efficiency; Cummulated daily flashes and viewtimes using a 49-day moving window to capture a full diurnal cycle (Boccippio et at., 2000); Cummulated flash rate density pentads (5-days). Quantile linear regression calculated for Regional Boxes:

16 Results 3) Decadal trends: Quantile linear regression: Method to estimate the change (trend) of flash rate density (FRD) quantiles as a function of the year; A quantile is a point taken from the inverse cumulative distribution function of the FRD so that, for examples, the 0.7 quantile is the value such that 70% of the pentad FRD have FRD below this value (70th percentile); K y t = 0 t k =1 k x tk t Q x t1,..., x tk =0 K Q y x t1,..., x tk = 0 k =1 k x tk t The coefficients k( ) are estimated for 19 different quantiles ( =0.05,0.10,...,0.95) using each time the entire dataset of a regional box.

17 Results 3) Decadal trends:

18 Results 3) Decadal trends: OLS -0.4 fl km (fl km-2) per Q(0.90) = 41.9 fl km-2-6% per year All quantile trends are significant at 10% level

19 Results 3) Decadal trends: Summary for Q(0.95): Circles = Land trend (or No Mask) Triangles = Ocean trend Blue = negative trend on the 95th percentile Red = positive trend on the 95th percentile only trends with 95% confidence are shown.

20 Results 3) Decadal trends: 13-years is a very small period be considered a climate trend. But, if it is a sign of global warming, warming how can we explain a decrease in the high flash rate densities? Convective mass flux and T relationship (Betts 1998; Held et al., 2006; Vecchi and Soden 2007): M c P = 0.07 T Mc P T Convective mass flux updraft lightning

21 Thank you!