Lesson 7: Hydrometeorological Hazards PDF

LESSON 7 Hydrometeorological Hazards HYDROMETEOROLOGY - is the study of the atmospheric and terrestrial phases of the hydrological cycle with emphasis on the interrelationship between them. It deals with the transfer of water and energy between land surface and the lower atmosphere. DIFFERENT TYPE...

LESSON 7 Hydrometeorological Hazards HYDROMETEOROLOGY - is the study of the atmospheric and terrestrial phases of the hydrological cycle with emphasis on the interrelationship between them. It deals with the transfer of water and energy between land surface and the lower atmosphere. DIFFERENT TYPES OF HYDROMETEOROLOGICAL HAZARDS Tropical cyclone is a rotating, organized system of clouds and thunderstorms that originates over the tropical waters. Tropical cyclones rotate in a counterclockwise direction in the northern hemisphere (conversely, clockwise in the southern hemisphere). The term tropical cyclone encompasses tropical depressions, tropical storms, typhoons and hurricanes.  The classification of tropical cyclones according to the strength of the associated winds as adopted by PAGASA (as of 01 May 2015) are as follows: TROPICAL DEPRESSION (TD) - a tropical cyclone with maximum sustained winds of up to 61 kph. TROPICAL STORM (TS) - a tropical cyclone with maximum wind speed of 62 to 88 kph. SEVERE TROPICAL STORM (STS) - a tropical cyclone with maximum wind speed of 89 to 117 kph. TYPHOON (TY) - a tropical cyclone with maximum wind speed of 118 to 220 kph SUPER TYPHOON (STY) – a tropical cyclone with maximum wind speed exceeding 220 kph. THE TROPICAL CYCLONE Tropical cyclone can be seen in a satellite image due to its characteristic spiral/circular shape. The stronger and more intense a tropical cyclone becomes, the more symmetrical the inner clouds or rain bands are and a distinctive “eye” at the center of circulation becomes visible. This means that a tropical cyclone tends to be more circular and its center will have a cloudless region. Weather forecasters use satellite images to track the movement and estimate the intensity of tropical cyclones. RADAR is an acronym which stands for Radio Detection and Ranging. A Radar sends out electromagnetic waves to the atmosphere that is then reflected by hydrometeors (e.g. rain, clouds) present in the sky. An image is created from the received signal and information on rain clouds can be gathered. While radar images give more details of a storm, it is limited to a range of approximately 400 km from the radar site  Once a tropical cyclone enters PAR, a 5-day forecast track (previously 3-day) is issued by PAGASA every 6 hours at 5am, 11am, 5pm and 11pm. A forecast track gives the expected location of a tropical cyclone in the succeeding 24- hour interval for the Together with the forecast track, PAGASA also issues the Public Storm Warning System (PSWS) to warn citizens of impending wind strength. The PSWS is as follows: Precautionary and safety measures for hydrometeorological hazards Tropical cyclones are hydrometeorological hazards characterized by strong winds and heavy rain. Every year, an average of 19 tropical cyclones enter the Philippine Area of Responsibility and approximately 9-10 make landfall in the Philippines. This is because the Philippines is located on the western rim of the Pacific Ocean, where most tropical cyclones pass. Tropical cyclones can have a forecast lead time of 5 days. Below is a list of things that you can do before, during and after the Below is a list of things that you can do before, during and after the passage of this type of weather disturbance. BEFORE DURING AFTER Coordinate with Regularly monitor Attend to injuries if local community or official updates of needed. barangay on safety PAGASA or other Apply first aid to plan during times reliable sources on minor cuts or of severe events the tropical wounds. Have a survival kit cyclone. Seek medical containing battery Stay in a sturdy assistance at your operated radio, and stable shelter nearest clinic or flashlight, Stay indoors and hospital. emergency away from Check your cooking windows or things immediate vicinity equipment, that may topple (house, school, candles, matches over. surroundings) for and first aid kit. Coordinate with any damages that Recommend the local can pose a trimming and community on potential hazard to removal of possible people around it. unstable trees, evacuation electric posts, or measures any infrastructure (especially if you that could fall and are in a low-lying Thunderstorms are generally local storms produced by cumulonimbus clouds and are always accompanied by lightning and thunder, usually with strong wind gusts, heavy rain and sometimes with hail and/or tornado. Thunderstorms are typical in warm environments like the tropics and may persist for 1 to 2 hours Below are some list of things that you can to do before, during and after a thunderstorm event. BEFORE DURING AFTER Learn about your Stay indoors and Continue area’s remain calm monitoring PAGASA thunderstorm risk Postpone all or local radio / by looking at past outdoor activities. television stations events. These risks Regularly monitor for weather differ for different official updates by updates places and PAGASA or other Always observe different months. reliable sources safety measures on Discuss how you Turn off and unplug if you need to go would know if a all electrical and outdoors. thunderstorm may electronic devices Stay away from produce light, storm-damaged moderate, heavy or areas. torrential rain as Flood is the overflowing of the normal confines of a stream or bodies of water, or the accumulation of water over areas that are not normally submerged. While flooding may last days or even Residents wait for rescuers at a building weeks, Flash Floods during flooding caused by Typhoon Ketsana in Cainta Rizal, east of Manila are also caused by September 27, 2009. heavy precipitation in a short period of time, usually less than 6 Below is a list of things that you can to do before, during and after a flooding event. BEFORE DURING AFTER Learn about your Unplug all electric and Report broken utility area’s flood risk by electronic devices lines (electricity, looking at past events. Listen continuously to water, gas, etc.) to These risks differ for official updates on appropriate agencies/ different places and weather and flooding. authorities. different months Remain calm and be Ensure that electrical Know the flood hazard ready in case appliances are map in your evacuation is checked by a community. necessary. competent electrician Learn from previous Do not to attempt to before switching them occurrences how cross flowing streams on. frequent, how high unless they are Stay away from flood and how fast flood can assured that the water waters. occur. is below knee level. It is possible to contract diseases from flood water. Storm surge is the rise and onshore surge of seawater as the result primarily of the winds of a tropical cyclone, and secondarily of the surface pressure drop near the center of the tropical cyclone. The height of storm surge is dependent on the size, intensity and movement of the tropical cyclone, shape of the coastline as well as nearshore underwater topography and astronomical tides. Below is a list of things that you can to do before, during and after a storm surge event. BEFORE DURING AFTER Learn about your Regularly monitor Check structural area’s vulnerability to official storm surge damage of your storm surge by advisory/forecast surroundings and looking at past events. updates of PAGASA make sure structures If vulnerable, Remain calm and be are safe from recommend relocation ready in case of collapsing. to safer grounds. evacuation. Check surroundings Stay away from Stay away from for electrical damage. beaches / shore during beaches / shore and Stay away from flood tropical cyclone low-lying areas. waters. passage. Head towards inland It is possible to Identify evacuation away from potential contract diseases from routes leading to safe flow of water. flood water. higher grounds. Turn off power supply. Uneven ground, open Establish evacuation If caught in a storm drainage and/or sharp plans and procedures. surge, you are advised debris under Participate actively in to hold on large floodwater can be the school drills on structures like big potentially harmful. disaster response. trees. Clean all mud and debris. EXTREME CLIMATE EVENT: El Niño is a significant increase in ocean temperature over the eastern and central Pacific Ocean. It occurs at irregular intervals ranging from 2-7 years usually developing in the early months of the year and decay the following year. In the Philippines, El Niño conditions are often  Below is a list of things that you can to do before, during and afterBEFORE El Niño condition. DURING AFTER Listen and monitor Avoid doing strenuous Seek medical attention if PAGASA El Niño/ activity during the hottest you or another person drought/dry spell forecast time of the day. experiences symptoms of on what parts of the Keep hydrated. heat stress. country will be affected During drought condition, severe conditions. conserve water. Plan your daily activities to Stay indoors whenever avoid doing strenuous possible. work during the hottest Regularly clean electric time of the day. fans and air conditioner Learn about the symptoms filters. of heat stress or exposure Wear light-colored and to extreme environmental lightweight clothing. heat, sunburn, heat Take frequent breaks if you exhaustion, heat stroke, must work outdoors. dehydration, and other related conditions caused by very hot climate by discussing with local physicians / medical personnel. HYDROMETEOROLOGICAL HAZARDS MAP Return period is the probability of an event such as heavy rain, intense typhoon of floods to happen. It is a statistical measurement mainly based on historical data that gives the estimated time interval between similar extreme events. Rainfall in the Philippines Rainfall is the most important climatic element in the Philippines. Rainfall distribution throughout the country varies from one region to another, depending upon the direction of the moisture-bearing winds and the location of the mountain systems. The mean annual rainfall of the Philippines varies from 965 to 4,064 millimeters  The Modified Coronas Climate Classification describes the monthly rainfall variations in different parts of the country. Aside from rain gauge monitoring in different parts of the Philippines, PAGASA publishes regularly updated color-coded satellite images from the Multi-Functional Transport Satellite or MTSAT (as of Dec 2015, but will soon shift to a newer satellite called Himawari-8) to visualize rain distribution across the country. Color code is as follows: Red – heavy rain Yellow – light to moderate rain White – clouds Weather Radar In addition to the satellite observation, PAGASA operates 10 weather radar stations (as of 2015) all over the Philippines. Weather radar can detect hydrometeors (e.g. rain, clouds) by transmitting electromagnetic radiation to the atmosphere then analyze the returning “echoes” reflected by weather elements present in the sky. Radar image over Bataan / NCR showing extensive rain. Another product of PAGASA is its watershed monitoring network or Flood monitoring system. Using water level sensors that measures the height of the water level of major river systems, users can monitor impending flooding in major river systems in the Philippines.  While we are usually concerned with heavy rainfall events, lack of rain is also a significant condition that we also experience. Weather in different parts of the Philippines can vary significantly for certain years as a response to changing global climate. One of the main climate drivers that affect the Philippines is the El Niño Southern Oscillation (ENSO) or simply El Niño. El Niño is a significant increase in ocean temperature over the eastern and central Pacific Ocean. It occurs at irregular intervals ranging from 2- 7 years usually developing in the early months of the year and decay the following year. In the Philippines,  Drought/Dry spell assessment is also regularly published to report unusual climate conditions in different parts of the Philippines. The Nationwide Operational Assessment of Hazards or NOAH is a program under the Department of Science and Technology (DOST) with the mission to undertake disaster science research and development, advance the use of cutting-edge technology and recommend innovative information services in government’s disaster prevention and mitigation efforts. The NOAH website displays the PAGASA radar data, rainfall measurements of rain gauges of DOST, and has flood hazard maps for different regions of the Philippines with 5-year, 25-year, 50-year and 100- year return periods. National Mapping and Resource Information Authority (NAMRIA) is an agency of the Philippine government under the Department of Environment and Natural Resources (DENR) responsible for providing the public with mapmaking services and acting as the On its website’s download page, central mapping http://www.namria.gov.ph/download.php, hazard/susceptibility maps for storm surge, rain- agency, depository, and induced landslide and flood are freely available. distribution facility of natural resources data in the form of maps, charts, texts, and The Mines and Geosciences Bureau (MGB), a government agency also under the Department of Environment and Natural Resources (DENR), is responsible for the conservation, management, MGB maintains a geohazard development and proper visualization portal accessible at this URL http:// use of the country’s gdis.denr.gov.ph/mgbgoogle/. mineral resources  END. 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