JMA s atmospheric motion vectors

Transcription

1 Prepared by JMA Agenda Item: WG II/6 Discussed in WG II JMA s atmospheric motion vectors This paper reports on the recent status of JMA's Atmospheric Motion Vectors (AMVs) from MTSAT-2 and MTSAT-1R, and gives an overview of Himawari-8 AMVs.

2 1 INTRODUCTION This working paper reports on the atmospheric motion vectors (AMVs) produced by the Meteorological Satellite Center (MSC) of the Japan Meteorological Agency (JMA) using images from MTSAT-1R and MTSAT-2. The status of AMV production and dissemination is covered in Section 2, MTSAT AMV quality is described in Section 3, the status of Himawari-8 AMVs and the related dissemination plan are outlined in Section 4, and the statistical characteristics of Himawari-8 AMVs compared to radiosonde observations and the first guess (FG) in JMA s NWP is discussed in Section 5. 2 STATUS OF MTSAT AMV PRODUCTION AND DISSEMINATION Table 1 lists the details of current MTSAT-2 AMV dissemination. JMA generates four types of AMVs: MTSAT-2 Infrared (IR: 10.8 micrometers), Water Vapor (WV: 6.8 micrometers), Visible (VIS: 0.63 micrometers) and Short-wave Infrared (IR4: 3.8 micrometers) images (referred to here as IR, WV, VIS and IR4 AMVs, respectively). IR, WV and VIS winds are disseminated via the Global Telecommunication System (GTS) in Binary Universal Form for Data Representation (BUFR) format. Table 1 MTSAT-2 Atmospheric motion vector products generated by AMV type Level of height * Infrared: IR (10.8 micrometer) Wator Vapor: WV (6.8 micrometer) Vissible: VIS (0.63 micrometer) Short-wave Infrared: IR4 (3.8 micrometer) Upper, middle, low Upper, middle Low Low Time (UTC) Image interval (minutes) Image sector 00, 06, 12, 18 Full disk , 08-11, 14-17, Northern Hemisphere 30 01, 07, 13, , 07-11, 13-17,19-23 Southern Hemisphere 60 00, 06, 12, 18 Full disk , 08-11, 13-17, Northern Hemisphere 30 01, 07, 13, , 07-11, 13-17,19-23 Southern Hemisphere 60 00, 06 Full disk , 08-09, Northern Hemisphere 30 01, , 07-09, Southern Hemisphere 60 12,18 Full disk , 14-17, Northern Hemisphere 30 07, 13, , 13-17, Southern Hemisphere 60 Distribution BUFR Ver.4 via GTS BUFR Ver. 4 via GTS BUFR Ver.4 via GTS Internal use only * Upper: above 400 hpa; middle: hpa; low: below 700 hpa Page 2 of 8

3 3 STATUS OF MTSAT AMV QUALITY IR upper-level and low-level AMVs This section reports on the monthly quality of six-hourly IR and WV AMVs produced from July 2005 to February 2014 based on standard CGMS AMV statistics. AMVs are compared with radiosonde observations for quality evaluation. Figures 1 and 2 show time-series representations of monthly statistics (number, root mean square vector difference (RMSVD) and wind speed bias (BIAS)) for upper-level (above 400 hpa) and low-level (below 700 hpa) IR AMVs. For these statistics, AMVs with quality indicator (QI) values above 0.85 were used. To match radiosonde observation times, AMVs at 00 and 12 UTC were used. Figure 1 shows that upper-level IR AMVs have slow biases that still remain in the winter hemisphere. Figure 2 shows that low-level IR AMVs have relatively small RMSVDs and BIASes (about 4 5 m/s and 0 1 m/s, respectively). This is because lower-level wind speeds are lower than upper-level ones (not shown). Figure 1: Long-term time-series representation of the number (upper part), RMSVDs and BIASes (lower part) of upper-level IR AMVs (QI > 0.85) over the Northern Hemisphere (between 20 N and 60 N; blue lines), the tropics (between 20 S and 20 N; red lines) and the Southern Hemisphere (between 60 S and 20 S; green lines). RMSVDs (solid lines) and BIASes (dashed lines) are shown. Page 3 of 8

4 Figure 2: As per Figure 1, but for low-level IR AMVs WV AMVs over cloudy areas Figure 3 is similar to Figures 1 and 2, but for high-level WV AMVs over cloudy regions. Positive wind speed BIAS values can be seen over all regions. Figure 3: As per Figure 1, but for cloudy-region WV AMVs Page 4 of 8

5 Prepared by JMA Agenda Item: WG II/6 Discussed in WG II 4 STATUS AND DISSEMINATION PLAN FOR HIMAWARI-8 AMVs JMA/MSC will begin the dissemination of Himawari-8 AMVs in July Computed AMV types and related specifications are shown in Table 2. From Himawari-8, upper- and middle-level AMVs computed from the 0.64 µm band will be provided. Spatial density for Himawari-8 AMVs will be doubled comparing to that of MTSAT-AMVs. To support a smooth user transition to Himawari-8 AMVs, both MTSAT and Himawari-8 AMVs will be disseminated in parallel until March 2016 via GTS (for operational winds) and JMA s FTP server. Table 2 Himawari-8 atmospheric motion vector products generated by Target Distribution AMV type Height Time Image interval size (pixels) 10.4 µm (IR) Upper, middle, low Hourly 10 minutes 7 x 7 BUFR via GTS 0.64 µm (VIS) Upper, middle, low Hourly 10 minutes 28 x 28 BUFR via GTS 6.2 µm (WV1) Upper (100 Hourly 10 minutes 7 x 7 BUFR via GTS 400 hpa) 6.9 µm (WV2) Upper, middle Hourly 10 minutes 7 x 7 BUFR via GTS ( hpa) 7.3 µm (WV3) Upper, middle, Hourly 10 minutes 7 x 7 BUFR via GTS ( hpa) 3.9 µm (IR) Upper, middle, low Hourly 10 minutes 7 x 7 Internal use only 5 Himawari-8 AMV QUALITY Table 3 shows radiosonde statistics for Himawari-8 and MTSAT AMVs for the period from January to February Quality is improved for upper and middle levels over the Northern Hemisphere and tropical regions. However, increases in BIAS and RMSVD are seen for middle level over the Southern Hemisphere.

6 Prepared by JMA Agenda Item: WG II/6 Discussed in WG II Table 3 Sonde statistics for Himawari-8 AMVs (left) and MTSAT-AMVs (right) Himawari-8 IR (10.4 µm) AMVs for Jan. 24 Feb MTSAT IR (10.8 µm) AMVs for Jan. 24 Feb Himawari-8 WV (band 8, 9,10) AMVs over a cloudy area MTSAT WV (cloudy) AMVs for Jan. 24 Feb

7 Figures 4 and 5 show the spatial and vertical distribution of Himawari-8 IR and WV AMVs against JMA s NWP first guess. For IR AMVs, a relatively large bias is observed over the southern part of the Chinese continent and in tropical areas. WV AMVs also show positive wind speed bias around tropical regions. Figure 4: O-B statistics for band 13 (10.4 µm) Himawari-8 AMVs (QI > 60) based on JMA s NWP first guess. The top column shows spatial distribution for the root mean square vector difference (RMSVD) and mean error (BIAS). The lower ones are the same but for vertical distribution. RMSVD is reduced, especially over sea areas, but relatively large RMSVD values (5 10 m/s) are seen over southern China and other land areas. Page 7 of 8

8 Figure 5: As per Figure 4, but for band 9 (WV, 6.7 µm) AMVs. An overall positive wind speed bias appears in tropical areas and the Southern Hemisphere. Himawari-8 AMVs are considered to increase wind vector divergence for NWP in upper levels. Page 8 of 8