MSGVIEW: AN OPERATIONAL AND TRAINING TOOL TO PROCESS, ANALYZE AND VISUALIZATION OF MSG SEVIRI DATA

Transcription

1 MSGVIEW: AN OPERATIONAL AND TRAINING TOOL TO PROCESS, ANALYZE AND VISUALIZATION OF MSG SEVIRI DATA Aydın Gürol Ertürk Turkish State Meteorological Service, Remote Sensing Division, CC 401, Kalaba Ankara, Turkey Abstract The SEVIRI (Spinning Enhanced Visible and Infrared Imager) instrument on the MSG (METEOSAT Second Generation) satellite has been producing high-resolution spectral, spatial and temporal data. SEVIRI instrument provides wide opportunities with its 11 narrow band infrared and visible channels in addition to one broadband visible channel for the researchers and forecasters. The Channel Difference and RGB Applications based on the physical features of SEVIRI channels can provide better visualization about the characteristic of the meteorological phenomenon. The possible usages of these applications are detection of cold and warm air mass, convective system, Cb tops, fog, dust and fire. MSGView software has been started to develop at EUMETSAT in 2004 and continued the developed at Turkish State Meteorological Service (TSMS) and being operationally used since 2006 at the forecast centers. This software has capabilities to analyze process and display U-MARF HDF5 formatted MSG SEVIRI data and being used national, international and EUMETSAT s training workshops as computer lab. The software is distributed as free of charge to support to the young and free meteorologists. In this study, MSGView software will present as its capabilities to display channel difference, RGB applications, scatter plot diagrams and other features. Evaluations of training workshops indicates that MSGView is very good tool to make easy the interpretation of MSG images. INTRODUCTION SEVIRI, used to support nowcasting and short term forecasting. In a day, the radiometer SEVIRI collects 96 images, with a frequency of one image per fifteen minutes. Each radiometer is a composite of eleven narrow-band channels in the following regions of the spectrum: solar (VIS), near infrared (NIR), water vapor (WV) and thermal infrared (IR). In addition, it includes one high resolution visible broad-band channel (HRV) with a sampling distance of 1km at the sub-satellite point (Schmetz at. al. 2002) MSGView is a MSG SEVIRI data processing and display software running on the MS Windows (XP, Vista AND Windows 7) platform, developed at the TSMS. The software has been developed to support operational meteorology and short term forecast and nowcasting. It has been running operationally at the Central Weather Forecast Center in Ankara and Istanbul, Izmir and Antalya Regional Forecast Center of TSMS since MSGView software has been announced in 2009 by EUMETSAT via web site and distributed as free of charge. About 50 users have been requested and downloaded the software all over the world. Figure 1 presents the interface of the software. It has a Main Menu, a wide Display and a Specification panel. The main target audiences of the software are forecasters, researchers and especially trainees of satellite meteorology. Even though MSGView has been developed for operational meteorology it can be used for satellite meteorology training. It has been used as a computer lab at the trainings

2 organized by EUMETSAT & TSMS. Usage is practical and it has many tools to make easy to understand physical background of the images. All images in this paper have been generated by using MSGView software. Figure 1: MSGView interface, full disc RGB321 image. MAIN FEATURES MSGView has been developed by using C++ for MS Windows platforms. It is easy to install with a setup file and no need powerful PC. MSGView software has a user friendly interface to make easy its usage. MSGView software supports Hierarchal Data File format version 5 (HDF5). In addition to this it supports also EUMETSAT archive system (UMARF) GEO HDF5 file format which makes useful it world-wide (HDF5 User s Guide, 2010). There are several alternatives while displaying MSG images. Those are: a. Full Disc Display (Displaying whole MSG disc) b. Partial Display (Displaying a part of MSG disc) c. Single Channel (Displaying a single channel like IR10.8, VIS0.6 etc.)

3 d. Channel Difference (Displaying Brightness Temperature or Reflectance differences of two SEVIRI channels.) e. RGB Composite (Displaying three MSG channels or channel differences as RGB composite) While displaying a single channel, grey scale or look-up table can be used with a proper scale. Additionally, it is possible to apply Land/Sea mask for better understanding of images. Selected area or whole image can be saved as a physical value (i.e. Brightness Temperature, Reflectance and Radiance). Single channel, channel differences or RGB composite image can be animated and save as a picture (JPEG or BMP format). MSGView software has also zoom feature and selected area can be zoomed as 2, 3 or 4 times. MSGView features have been developed to perform recommendation of the forecasters and in the MSG Interpretation Guide which was prepared by EUMETSAT. Specifications Panel Specifications panel (Figure 1 on the left) is the most important part of the software. Before make a display, all necessary specifications about image should be arranged on this panel. Center of the image is determined using Latitude and Longitude edit box. To display single channel, RGB or channel difference image the channels is selected appropriate selection boxes. Look-up tables had been filled in the color table combo box and can be selected. When working directory selected, MSG files is come into list box. To add a cycle in an animation, check box on the right of MSG cycle name should be checked. Overlay, animation tools and some other features are also placed on the specifications panel. IR-VIS Channel Applications IR images with or without look-up table are crucial to detect convective cloud tops. There are some appropriate color table available in MSGView software is to detect convective storms evidently. Figure 2 (on the left) presents detection of Cold U/V storm and (on the right) Cold Ring Shape storm. Figure 2: (left) 5 Nov 2007, GMT METEOSAT 9 IR10.8 Image. Thunderstorm over Southwestern coast of Turkey, (right) 26 October 2009, GMT METEOSAT 9 IR10.8 image. Cold ring shape storm over Cyprus. High resolution visible channel (HRV) is also useful for understanding cloud top features. MSGView serves a very good HRV display especially with grey scale. Figure 3 shows a convective cloud top example of HRV image. Gradient waves and cirrus plumes are well seen with this image.

4 Figure 3: 5 November 2007, GMT METEOSAT 9 HRV Image. Channel Difference Application MSG Infrared channel difference is used detection of the fog and dust storms. Figure 4 presents how to detect fog using channel difference application and Figure 5 presents detection of dust storms. a b c Figure 4: Fog at Po Valley. MSG 2, 1 December :45 UTC. A) channel IR3.9, b) channel IR10.8, c) differences between channel IR3.9 and channel IR10.8. a b c Figure 5: Dust storms over Middle East. MSG 2, 25 June :45 UTC. A) channel IR8.7, b) channel IR10.8, c) differences between channel IR8.7 and channel IR10.8 and d) Dust RGB.

5 RGB Application RGB is one of the most useful tools to make better interpretation of the MSG images. Using RGBs it is possible to recognize snow cover, fog, cloud phase, multi layer clouds, storms, dust, ash cloud and other meteorological phenomenas. MSGView has a easy interface to select simply three SEVIRI channels and to display RGB image. Additionally differences RGB s recommended by EUMETSAT are in the combo box and can be display subject to select (MSG Interpretation Guide, 2006). Figure 6 presents some RGB examples. a b c d Figure 6: a) RGB321 snow over Alpines, b) Fog RGB, fog over Po Valley c) Storms RGB, Cold Ring shape storm over Cyprus, d) Ash RGB, ash cloud over Europe. Customization of RGB There is another feature to make specific channel difference and also difference RGB with using special scales. User customized the MSG channels focusing on the meteorological events. This tool gives flexibility to users to apply hundreds of channel difference RGB application with many different scales. Scatter Plot Diagrams Last but not least, MSGView has a feature to display scatter plot diagram which draws scatter plot of selected area from Storms, Air Masses, Dust and Ash RGB images. BTD, BT or differences of Reflectance for SEVIRI channels can be plotted to make well understand meteorological phenomena quantitatively. It is also useful to determine the thresholds and clusters. Figure 7 shows a squall line over Saudi Arabia with variation of SEVIRI channels Brightness Temperature and their differences as an example of scatter plot diagram. It makes easy to recognize storms in a pixel base.

6 Figure 7: Scatter plot diagram for deep convection over Saudi Arabia. Deep convection (yellow) reflectance differences of VIS06 and NIR16 is around %35-45, BT of IR108 is around K, BTD of WV channels is around -3 and 1 K and BTD of WV62 and IR108 is around -2 and 2 K. CONLUSION MSGView software has been using since 2006 at TSMS s forecast centers to support operational meteorology, aviation forecast, short term forecasting and nowcasting. Since then it makes more useful MSG images and application to forecasters. It has many useful features and short-cuts to give more time to the users to analysis MSG images efficiently. Due to it works a real data (not image) it also serves to user understanding of quantitative information about MSG images. MSGView has some features such that scatter plot diagrams, saving quantitative information, gives a crucial opportunity to the researchers for their study. MSGView beside its operational usage at the forecast centers, it is a kind of training tool. While preparing images (single, channel difference or RGB) trainee can understand easily physical background of the MSG SEVIRI channels. This software is also recommended to use as a computer lab in the training workshops. Another distinguish advantage of this software is that freely distributed. It makes that more users can have benefit to use MSG images in their works. REFERENCES HDF5 User s Guide (2010): MSG Interpretation Guide (2006): Schmetz, J., Pili, P., Tjemkes, S., Just, D., Kerkmann, J., Rota, S., and Ratier, A. (2002), An Introduction to MSG. Bull. Amer. Meteor. Soc., Vol. 83, No. 7,