Measurements from Geostationary Satellite

Transcription

1 The Fifth Asia/Oceania Meteorological Satellite Users' Conference (2014) Characteristics of Multi-spectral Measurements from Geostationary Satellite during Convections over North China Lin Yinjing Severe Weather Prediction Center National Meteorological Center of CMA

2 OUTLINE Background Data processing methodology Characteristics of multi-spectral measurements during convections Locations of severe convective weather Intensity of short-time heavy rainfall Summary

3 Background

4 Background IR1(10.3~11.5μm) 11 WV(6.3~7.6μm) VIS(0.5~0.9μm)

5 Data processing methodology FY2E Channels Wavelength Special resolution Visible (VIS) 0.5~0.9μm 1.25km Mid-Infrared (MIR) 3.6~4.1μm Temporal resolution Water Vapor (WV) 6.3~7.6μm 6μm 30min 5km Infrared 1 (IR1) 10.3~11.5μm Infrared 2 (IR2) 11.6~12.8μm IR1 channel brightness temperature (BT IR1 ) Brightness temperature difference between WV and IR1 channel (BT -BT Soden and Bretherton,1993; Schmetz et al., 1997; WV IR1 ) Mecikalski and Bedka, 2006 Height of cloud tops

6 VIS albedo (VIS) Thickness of clouds Normalization methods: Cheng et al. 1993; King et al. 1995; Behrangi et al Minnis and Harrison 1984; Tsonis and Isaac 1985 Wang 2009 QLSA Zhuge et al Thickness of clouds

7 MIR channel (3.6~4.1μm) reflectivity (MIRRef) Calculate MIR channel reflectivity by striping off emitted radiation from the received radiance. ( Setvak and Doswell 1991 ) MIRRef Particle size of cloud tops

8 cloud water content index (CWCI) Defined by combining NVIS ( thickness of the clouds ) and MIRRef(Particle size of cloud tops) Cloud water Cloud water content of clouds

9 Data processing methodology Characteristics of clouds Multi-spectral measurements Height of cloud tops IR1 channel brightness temperature (BT IR1 ) Brightness temperature difference between IR1 and WV channel (BT WV -BT IR1 ) Thickness of cloud tops Particle size of cloud tops Cloud water content Normalized VIS channel albedo (NVIS) MIR channel reflectivity (MIRRef) Cloud water content index, NVIS/IR4Ref (CWCI)

10 Cases 23 Jun, Jul, AM~11PM on 23 Jun, 2011 (Local time) 2PM on 24 Jul,2011~ 2AM on 25 Jul,2011 (Local time)

11 :00 500hPa wind + Temperature Cold air at 500hPa; Strong mid-level wind; Strong vertical wind shear 500hPa wind +0-6km vertical wind shear

12 :00 500hPa wind + Temperature No cold air in middle atmosphere; Weak vertical wind shear 500hPa wind +0-6km vertical wind shear

13 Cases

14 Locations of severe convective weather 6.23 BT IR1 (Colors), BT WV -BT IR1 (Contour lines), Short-time heavy rainfall ( 20mm/h----Blue + ; 50mm/h----Red + ; 80mm/h----Magenta + )

15 Locations of severe convective weather 6.23 BT IR1 (Colors), NVIS(Contour lines), Short-time heavy rainfall (+), hail(red triangle) and high wind(blue wind shaft) 11:00 12:00 13:30 11:00 12:00 13:30 In the case with strong wind shear, the locations of convective weather are g, close to cloud tops (Low BT IR1 ) and thick clouds (High NVIS) in initial stage of convection.

16 Locations of severe convective weather 6.23 BT IR1 (Colors), NVIS(Contour lines), Short-time heavy rainfall (+), hail(red triangle) and high wind(blue wind shaft) 15:30 16:30 17:00 15:30 16:30 17:00 Gradually, cloud tops (Low BT IR1 ) move to the downwind of thick cloud (High y, p ( IR1) ( g NVIS) because of the slantwise development of convection, and convective weather occurs near the thick cloud.

17 Locations of severe convective weather :30 13:30 14:30 15:30 In the case with weak vertical wind shear, which means the convection nearly In the case with weak vertical wind shear, which means the convection nearly develop vertically. Convective weather happens nearby the highest cloud tops (Low BT IR1 ) and the thickest clouds (High NVIS).

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19 Intensity of short-time heavy rainfall The intensity of short-time rainfall has poor relationship with BT IR1, The e te s ty o s o t t e a a as poo e at o s p t IR1, e minimum MIRRef of the entire cloud is used to measure the particle size of cloud top, and the heavier short-time rainfall, the smaller MIRRef.

20 Intensity of short-time heavy rainfall m/h) INFALL(mm 1H RAI MIN MIRRef(%)

21 Intensity of short-time heavy rainfall Cloud Water Content Index

22 Intensity of short-time heavy rainfall m/h) INFALL(mm 1H RAI

23 Summary Five parameters are calculated or retrieved from FY2E data, including BT IR1, BT IR1 -BT WV, NVIS, MIRRef and CWCI, to measured height, thickness, particle size and water content of clouds separately. The convective clouds with large VIS and COT also have coldest BT IR1 and BT IR1 -BT WV in some cases with weak 0~6km vertical wind shear, which means the convection nearly develop vertically. In these cases convective weather happens nearby the highest cloud tops and the thickest clouds. I th ith t i d h th l ti f ti In other cases with strong wind shear, the location of convective weather is also close to cloud tops and thick clouds in initial stage of convection. But cloud tops move to the downwind of thick cloud gradually, because of the slantwise development of convection, and convective weather occurs between them.

24 Summary The minimum IR4Ref of the entire cloud is used to measure the particle size of cloud top, and the heavier short-time rainfall, the smaller MIRRef. CWCI shows that the intensity of short-time rainfall has good relationship with the cloud water content, instead of the height of cloud top.

25 FUTURE Data processing methodology NVIS: Other normalization methods CWCI MIRRef More cases study and statistics research FY2F 6-min rapid scan data FY4: 14 channels

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