versely proportional with rainfall, the volume of rain was almost independent of rainfall. ..... begin to fall at a rate of a few centimeters per second. However .... The first theory involved the idea of a cyclone, a revolving cylinder of air with a more ..... circular arcs with a radius of curvature somewhat greater than that of the Earth.
A L -M USTANSIRIYAH U NIVERSITY
Characteristics of Rainfall over Iraq using TRMM Satellite-Borne Radar
A Thesis Submitted to the College of Science, Al-Mustansiriyah University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Atmospheric Sciences By
Munya F. A L -Z UHAIRI B. Sc. Atmospheric Sciences (2005) M. Sc. Atmospheric Sciences (2011) Supervised by Dr. Kais J. A L -J UMAILY Dr. Ali M. A L -S ALIHI Professor Assistant Professor
January, 2017
i
It is my deepest gratitude and warmest affection that I dedicate this thesis to my professor and supervisor
Professor Dr. Kais J. Al-Jumaily for his constant source of science, knowledge and inspiration . . .
Munya
ii
Acknowledgements First and foremost, I thank Allah for bringing me his grace and mercy; and without his blessings it would not have been possible that all my wishes and dreams to come into reality. I am forever grateful to my God. I would like to express my sincere thanks and deepest gratitude and appreciation to my supervisor Professor Dr. Kais Jamil Al-Jumaily for suggesting and supervising this work, and for his precious comments, motivation, encouragement, and guidance throughout my years of study and research. His continual, support and excellent supervision has been of great value for me and for this research. I also express my deep gratitude to my supervisor Assistant Professor Dr. Ali Mohammed Al-Salihi for his guidance and constant support throughout the time of my research. Without his support, I would not have been able to complete this work. I would like to express my thanks to the Administration of the Department of Atmospheric Sciences and the College of Science for giving me the chance to complete my study. I am also grateful to all staff and friends in Department of Atmospheric Sciences who gave me support and encouragement during the times of this study. I acknowledge the use of data from TRMM, JAXA, and NASA. Finally, my special thanks, and deepest love, and gratitude go to all my family members; my parents, my brothers, my sister and my aunt for their encouragement, constant support and patience during my study.
iii AL-MUSTANSIRIYAH UNIVERSITY
Abstract College of Science Department of Atmospheric Sciences Doctor of Philosophy Characteristics of Rainfall over Iraq using TRMM Satellite-Borne Radar by Munya F. A L -Z UHAIRI
Precipitation is one of the more difficult observational challenges of meteorological parameter to measure due to its spatial and temporal variability. The main techniques used to measure precipitation are rain gauges, radar, and satellites. Each technique has its own advantages, and disadvantage. Satellite is the only instrument that is able to obtain data for rainfall over land and water. The use of satellite-derived products to estimate precipitation over land is important for monitoring the spatial and temporal distributions of precipitation. The aim of this research is to use the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) measurements to study rainfall characteristics over Iraq through determination of composite climatology, spatiotemporal patterns, and vertical structure of convective rain storms. TRMM PR precipitation measurements were analyzed for the zone bounded by longitude 38-50o E and latitude 28-38o N. The results of diurnal means indicated that the contribution from MCSs to precipitation is higher than from thunderstorms and in the afternoon the contribution from MCSs reaches its minima while contribution from thunderstorms reaches its maxima. Analysis of monthly means showed that during the rainy season the contributions to precipitation from the MCSs were higher than that from the thunderstorms while during summer months the precipitation was mainly a result of thunderstorms activities that sometimes occur over the region, particularly in the north and north eastern part of the region. Comparisons between precipitation contributions from 20, 30, and 40 dBz radar reflectivity indicated that the contribution from 20 dBz reflectivity is higher than that from 30 dBz, and 40 dBz reflectivity suggesting that main precipitation rates is a light rain. The contributions of reflectivity values were increasing with altitude until reaching their peaks at certain height (around 2 km) then they were decreasing all the way up. The peak of 20 dBz is slightly higher than those
iv of 30 and 40 dBz. This is due to the fact that precipitation rates at the bottom of the cloud are always higher than those at higher levels. Maps of 14 years monthly rainfall anomalies for eight stations in Iraq illustrated that rainfall rate was oscillating between increasing and decreasing from one year to another and from month to month. Also rainfall depends on geographical location and nature of the region. No distinctive trend could be observed, but in general, there was an increasing in rainfall (positive anomalies) in one to three rainy seasons among the 14 years period. It was notable that there was almost no rain over Nukhuyb and Nasiriyah, stations for seven consecutive years (2004-2010). Analysis of 100 extreme rain events showed that rain size parameter was inversely proportional with rainfall, the volume of rain was almost independent of rainfall. The radar echo top was slightly decreasing with increasing rainfall, and the top of 30 dBz was increasing with rainfall. Analysis of high resolution TRMM data showed the near surface radar reflectivity factor (Z) and 10 km vertical Z display have a positive relation since the near surface reflectivity depends on the vertical extent of radar reflectivity.
v
Contents Acknowledgements
ii
Abstract
iii
List of Abbreviations
x
List of Symbols 1
2
xii
General Overview 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 The Growth of Precipitation Particles . . . . . . . . 1.2.2 Precipitation systems . . . . . . . . . . . . . . . . . . 1.3 Precipitation Measuring Techniques . . . . . . . . . . . . . 1.3.1 Rain Gauges . . . . . . . . . . . . . . . . . . . . . . . 1.3.2 Weather Radar . . . . . . . . . . . . . . . . . . . . . 1.3.3 Satellite . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Satellite Precipitation Estimates . . . . . . . . . . . . . . . . 1.4.1 Global Precipitation Measurement Mission . . . . . 1.5 Principles of Radar Meteorology . . . . . . . . . . . . . . . 1.5.1 Main Components of Weather Radar . . . . . . . . . 1.5.2 The Radar Equation . . . . . . . . . . . . . . . . . . 1.5.3 Weather Radar Equation . . . . . . . . . . . . . . . . 1.5.4 Relation of Reflectivity Factor to Precipitation Rate 1.5.5 Radar Display . . . . . . . . . . . . . . . . . . . . . . 1.6 Review of Previous works . . . . . . . . . . . . . . . . . . . 1.7 Aim of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 Thesis Outlines . . . . . . . . . . . . . . . . . . . . . . . . . Tropical Rainfall Measuring Mission 2.1 A Short History of TRMM . . . . . . . . . . . . . . . . . . 2.2 Description of The TRMM Instruments . . . . . . . . . . 2.2.1 Precipitation Radar (PR) . . . . . . . . . . . . . . . Precipitation Radar Major Functions . . . . . . . . Outline of The Precipitation Radar Operation . . . 2.2.2 TRMM Microwave Imager (TMI) . . . . . . . . . . 2.2.3 Visible and Infrared Scanner (VIRS) . . . . . . . . 2.2.4 Lightning Imaging Sensor (LIS) . . . . . . . . . . . 2.2.5 Cloud and Earth Radiant Energy System (CERES) 2.3 TRMM Algorithms . . . . . . . . . . . . . . . . . . . . . .
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44 48 49 50 51 51 52
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54 54 54 54 55 58 61 63 65 66 71
4
Case Studies of Extreme Rain Events 4.1 Analysis of Top 100 Rain Events . . . . . . . . . . . . . . . . . . . . . 4.2 Analysis of High Resolution TRMM PR Data . . . . . . . . . . . . . 4.3 Comparisons between Satellite and Ground Data . . . . . . . . . . .
77 77 81 90
5
Conclusions and Suggestion for Future Works 5.1 Conclusions . . . . . . . . . . . . . . . . . . 5.1.1 Climatological Analysis of Rainfall . 5.1.2 Case Studies of Extreme Rain Events 5.2 Suggestions for Future Works . . . . . . . .
95 95 95 97 97
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2.3.1 TRMM Precipitation Radar Algorithms . . . . . 2.3.2 TRMM Microwave Imager Algorithms . . . . . 2.3.3 TRMM Visible and Infrared Scanner Algorithm 2.3.4 TRMM Combined Algorithms . . . . . . . . . . TRMM Precipitation Radar Display Systems . . . . . . 2.4.1 Giovanni TOVAS . . . . . . . . . . . . . . . . . . 2.4.2 THOR . . . . . . . . . . . . . . . . . . . . . . . .
Climatological Analysis of Rainfall 3.1 Data and Methodology . . . . . . . . . . . . . . . 3.2 Main Characteristics of Precipitation System . . 3.2.1 Diurnal Distribution of Precipitation . . . 3.2.2 Seasonal Distribution of Precipitation . . 3.2.3 Annual Distribution of Precipitation . . . 3.2.4 Distribution of Precipitation System . . . 3.2.5 Vertical Structure of Precipitation System 3.3 Composite Climatology of Rainfall . . . . . . . . 3.3.1 Analysis of Monthly Rainfall . . . . . . . 3.3.2 Analysis of Annual Rainfall . . . . . . . .
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List of Figures
1.1 1.2 1.3 1.4 1.5 1.6
Rain gauges sited at a weather station . . . . . Weather Radar . . . . . . . . . . . . . . . . . . . Conceptual diagrams of Meteorological Radar An example of PPI display . . . . . . . . . . . . An example of RHI display . . . . . . . . . . . An example CAPII display . . . . . . . . . . . .
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2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11
TRMM satellite . . . . . . . . . . . . . . . . . . . . . . . . TRMM instrumentation and measurement path diagram Precipitation Radar . . . . . . . . . . . . . . . . . . . . . . Measurement concept of TRMM precipitation radar . . . TRMM Microwave Imager . . . . . . . . . . . . . . . . . . Visible Infrared Scanner . . . . . . . . . . . . . . . . . . . Lightning Imaging Sensor . . . . . . . . . . . . . . . . . . Cloud and Earth Radiant Energy System . . . . . . . . . . TRMM algorithms flow diagram . . . . . . . . . . . . . . TRMM precipitation radar algorithms flow . . . . . . . . THOR main window . . . . . . . . . . . . . . . . . . . . .
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30 32 33 37 39 41 42 43 45 47 53
3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20
Distribution of hourly precipitation . . . . . . . . . . . . . . . . . . Precipitation contribution from Thunderstorms and MCSs . . . . . Seasonal distribution of precipitation . . . . . . . . . . . . . . . . . . Distribution of monthly precipitation . . . . . . . . . . . . . . . . . Monthly Precipitation contribution from Thunderstorms and MCSs Annual hourly distribution of precipitation . . . . . . . . . . . . . . Annual diurnal variations of precipitation . . . . . . . . . . . . . . . Annual seasonal variations of precipitation . . . . . . . . . . . . . . Mean annual distribution of precipitation . . . . . . . . . . . . . . . Cumulative distribution of precipitation . . . . . . . . . . . . . . . . Seasonal rainfall contribution . . . . . . . . . . . . . . . . . . . . . . Diurnal and seasonal variations of precipitation 20 dBz . . . . . . . Diurnal and seasonal variations of precipitation 40 dBz . . . . . . . Vertical profiles of TRMM PR reflectivity . . . . . . . . . . . . . . . Locations of selected stations in Iraq . . . . . . . . . . . . . . . . . . Anomaly of monthly rainfall rate (mm/month) over Mosul . . . . . Anomaly of monthly rainfall rate (mm/month) over Sulaymaniyah Anomaly of monthly rainfall rate (mm/month) over Anah . . . . . Anomaly of monthly rainfall rate (mm/month) over Baghdad . . . Anomaly of monthly rainfall rate (mm/month) over Rutba . . . . .
55 56 57 57 58 59 60 60 61 62 63 64 64 65 67 67 68 68 69 70
viii 3.21 3.22 3.23 3.24
Anomaly of monthly rainfall rate (mm/month) over Nukhuyb . . . Anomaly of monthly rainfall rate (mm/month) over Nasiriyah . . Anomaly of monthly rainfall rate (mm/month) over Basrah . . . . Mean annual rainfall rate (mm/year) over Iraq for the period 20002013 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.25 Anomaly of annual rainfall rate (mm/year) over Iraq for 2000-2004 3.26 Anomaly of annual rainfall rate (mm/year) over Iraq for 2005-2009 3.27 Anomaly of annual rainfall rate (mm/year) over Iraq for 2010-2013 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14
70 71 72 73 74 75 76
Rain size for top 100 rain events for 1998-2011 . . . . . . . . . . . . 78 Rainfall for top 100 rain events for 1998-2011 . . . . . . . . . . . . . 79 Volume of rain for top 100 rain events for 1998-2011 . . . . . . . . . 80 Echo top for top 100 rain events for 1998-2011 . . . . . . . . . . . . . 82 Top of 30 dBz for top 100 rain events for 1998-2011 . . . . . . . . . . 83 Scatter plots of rainfall versus rain size . . . . . . . . . . . . . . . . . 84 TRMM swath one for 17/11/2009 . . . . . . . . . . . . . . . . . . . . 85 TRMM swath two for 17/11/2009 . . . . . . . . . . . . . . . . . . . 86 TRMM swath three for 17/11/2009 . . . . . . . . . . . . . . . . . . . 87 Near surface Z and Vertical view of Z for three case studies (17/11/2009, 12/12/2010, and 29/4/2011) . . . . . . . . . . . . . . . . . . . . . . 88 Near surface Z and Vertical view of Z for three case studies (25/12/2012, 28/1/2013, and 27/1/2014) . . . . . . . . . . . . . . . . . . . . . . . 89 TRMM, and IMSO rainfall measurements on 25/12/2012 . . . . . . 92 TRMM, and MoA rainfall measurements on 28/10/2015 . . . . . . 93 TRMM, IMSO, and MoA rainfall measurements on 29/10/2015 . . 94
ix
List of Tables
1.1 1.2 1.3 1.4 1.5
Atmospheric scale classification . . . . . . . . . . . . . . Scales of precipitation systems . . . . . . . . . . . . . . Typical frequencies and wavelengths of radar bands . . Examples of the relationship between Z and R for rain . Interpretation of the radar reflectivity scale . . . . . . .
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The main characteristics of the TRMM satellite TRMM PR system parameters . . . . . . . . . . TMI system parameters . . . . . . . . . . . . . VIRS system parameters . . . . . . . . . . . . . LIS system parameters . . . . . . . . . . . . . . CERES system parameters . . . . . . . . . . . . TRMM products definition . . . . . . . . . . . . TRMM standard PR algorithms . . . . . . . . . TRMM standard TMI algorithms . . . . . . . . TRMM standard VIRS algorithms . . . . . . . . TRMM standard COMB algorithms . . . . . .
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The geographical parameters for selected stations . . . . . . . . . .
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Parameters of rainfall measurements by TRMM PR for different case studies . . . . . . . . . . . . . . . . . . . . . . . . . . .
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List of Abbreviations AMSU ARC AVHRR CAMS CAPPI CCN CDF CERES COMB CRT DJF DMSP EOS GES DISC Giovanni GPCC GPI GPM GSFC IDL IFOV IMSO ITCZ JAXA JJA LEO LIS MAD MAM MCC MCSs MHS MoA MODIS NASA NOAA NWP PFs PPI
Advanced Microwave Sounding Unit Active Radar Calibration Advanced Very High Resolution Radiometer Climate Assessment and Monitoring System Constant Altitude PPI Cloud Condensation Nuclei Cumulative Distribution Function Clouds and Earth Radiant Energy System Combined Cathode Ray Tube December, January, and February Defense Meteorological Satellite Program Earth Observing System Goddard Earth Sciences Data and Information Services Center GES DISC Interactive Online Visualization and Analysis Infrastructure Global Precipitation Climatology Center Geosynchronous Precipitation Index Global Precipitation Measurement Goddard Space Flight Center Interactive Data Language Instantaneous Field Of View Iraqi Meteorological and Seismology Organization Inter Tropical Convergence Zone Japan Aerospace Exploration Agency June, July, and August Low Earth Orbit Lightning Imaging System Mean Absolute Difference March, April, and May Mesoscale Convective Complex Mesoscale Convective Systems Microwave Humidity Sounder Ministry of Agriculture Moderate Resolution Imaging Spectroradiometer National Aeronautics and Space Administration National Oceanic and Atmospheric Administration Numerical Weather Prediction models Precipitation Features Plan Position Indicator
xi PPS PR PRF PRI PWR RADAR RHI SON SSM/I SSMIS SST THOR TMI TMPA TOVAS TRMM VIRS
Precipitation Processing System Precipitation Radar Pulse Repetition Frequency Pulse Repetition Interval Passive Microwave Retrieval RAdio Detection And Ranging Range Height Indicator September, October, and November Special Sensor Microwave/Imager Special Sensor Microwave Imager Sounder Sea Surface Temperature Tool for High- resolution Observation Review TRMM Microwave Imager TRMM Multi-Satellite Precipitation Analysis TRMM Online Visualization and Analysis System Tropical Rainfall Measuring Mission Visible and Infrared Radiometer System
xii
List of Symbols At Ae c D fr G h k K L m n Pr P¯r Pt r ro rmax R TA TB t V Z λ ν σ τ θ
Target area Antenna aperture area Speed of light Particle diameter Pulse repetition frequency Antenna axial gain Pulse length Absorption cofficient Complex refractive term Liquid water content Complex refractive index Refractive index Received power Average received power Transmitted power Target range Particle radius Maximum unambiguous range Rainfall rate Antenna Temperatures Brightness Temperatures Time Resolution volume Radar Reflectivity Wavelength Radio frequency Backscatter cross-section Pulse duration Beamwidth
1
Chapter 1 General Overview 1.1
Introduction
Precipitation is an important meteorological parameter, which affects the hydrological cycle of the land surface, climate and global heat circulation. Understanding of rainfall distribution, amount and its intensity can improve protection of the environment and knowledge of physical processes of land, ocean and atmosphere (Kidd, 2001). Precipitation is usually classified as a convective or stratiform precipitation. Convective precipitation is usually associated with cumulus and cumulonimbus clouds that have a significant vertical velocity within it, which keeps the cloud droplets inside the cloud, enhancing their growth until the vertical currents are not able to counteract the force of gravity any longer and precipitation is produced. Stratiform precipitation is produced mainly by nimbostratus and sometimes by stratocumulus/altocumulus clouds. In these clouds, the vertical velocity is lower than inside the convective clouds, and it cannot prevent cloud droplets from falling earlier. The result is a smaller raindrop in these clouds (Houze Jr., 1993). Rainfall comprise the main source of water for the terrestrial hydrological processes, exact measurement and prediction of the spatial and temporal distribution of rainfall is a basic goal in hydrology (Shuttleworth, 2012). Rainfall is measured using various methods as rain gauges, radar and satellites, measuring rainfall with conventional or remote sensing techniques is particularly challenging due to the high spatial and temporal variability of precipitation. The rain gauge networks and ground-based weather radar are covered a limited places and are available only over land. Radar covered areas are larger than when rain gauge covered it, the maximum range of radars coverage is about 300 km. Only satellite instruments are able to make rainfall measurements over remote areas of land or water where data is difficult or impossible to collect (Shuttleworth, 2012).
Chapter 1. General Overview
2
The use of satellite-derived products to estimate precipitation over land is important for monitoring the spatial and temporal distributions of precipitation (Kidd, 2001). The Tropical Rainfall Measuring Mission (TRMM) is a joint mission between the National Aeronautics and Space Administration (NASA) of the United States and the Japan Aerospace Exploration Agency (JAXA) of Japan. The satellite was launched in November 27, 1997 and is currently continuing to operate. The objectives of TRMM are to measure rainfall and energy (i.e., latent heat of condensation) exchange of tropical and subtropical regions of the world from the space. TRMM is the first space mission dedicated to measure tropical and subtropical rainfall through microwave and visible/infrared sensors, including the first space borne rain radar (National Research Council, 2006).
1.2
Precipitation
Water may take a number of different forms in the atmosphere. These forms are collectively termed ‘precipitation’, which includes rain, drizzle, sleet (partly melted snowflakes, or rain and snow falling together), snow and hail. The intensity and duration of precipitation are extremely variable in most areas of the world. The source of precipitation is water vapor, which is always present in the atmosphere in varying amounts, although it makes up less than 1% by volume. However, the water vapor in the air must be cooled to allow water to be condensed into cloud droplets. These droplets then grow to form precipitation particles. The mass of water in the atmosphere in both liquid and vapor forms is around 1.3 × 1016 kg, compared with the mass of water in the oceans of around 1.3 × 1021 kg. Nevertheless, this water is distributed very unevenly, and is transported by the circulation of the atmosphere (Nace, 1967). A basic classification of atmospheric systems is shown in Table (1.1) (Nace, 1967). TABLE 1.1: Atmospheric scale classification (Nace, 1967).
Synoptic Period (hr) >48 Wavelength (km) >500
Mesoscale 1-48 20-500
Microscale
