Precipitation Group 1 CEC41S3 PDF

PRECIPITATION Group 1 - CEC41S3 ICE BREAKER Four May Shawn “Formation”  ment Meh sure “Measurement” Harith Mythic “Arithmetic” Lat Tea Tude “Latitude” East...

PRECIPITATION Group 1 - CEC41S3 ICE BREAKER Four May Shawn “Formation”  ment Meh sure “Measurement” Harith Mythic “Arithmetic” Lat Tea Tude “Latitude” East No “Snow” WHAT IS PRECIPITATION? is the general term for all forms of moisture emanating from the clouds and falling to the ground.  TOPIC OUTLINE 1. 2. 3. 4. 5. Formation and Measurement Interpretation of Variation in Snow Cover Forms Precipitation Data Precipitation and Snow Fall FORMATION AND FORMS Formation of Precipitation Precipitation forms in the clouds when water vapor condenses into bigger to bigger droplets of water. Formation of Precipitation Dust, soot from fires and vehicle exhaust, sea salts, volcanic eruptions, etc. about 1/100th the size of a cloud droplet Formation of Precipitation  Types of Precipitation 1. Convective Precipitation 2. Cyclonic Precipitation 3.Orographic Precipitation  Types of Precipitation 1. Convective Precipitation Due to intense heating of air at the ground which leads to expansion and vertical rise of air.  Types of Precipitation 2. Cyclonic Precipitation Associated with the movement of large air- mass systems, as in the case of warm of cold fronts  Types of Precipitation 2. Cyclonic Precipitation Warm Front Warmer air-mass that is advancing into a cooler air- mass.  Types of Precipitation 2. Cyclonic Precipitation Cold Front Movement of cooler air- mass into an area of warmer air-mass. Types of Precipitation SYMBOLS:  Types of Precipitation 3. Orographic Precipitation Lifting of moist air masses over the windward side of mountain ranges  Forms of Precipitation Rain Drizzle  Forms of Precipitation Glaze Sleet  Forms of Precipitation Snow Hail Artificially Induced Precipitation Artificial rain, also known as cloud seeding is what's known as a weather modification technique. It artificially alters the weather by enhancing the ability of clouds to produce so-called “artificial rain” or snow, which can help meet the precipitation needs of a particular region. Artificially Induced Precipitation  Artificially Induced Precipitation Advantages of Cloud Seeding Disadvantages of Cloud Seeding Creates rain It uses chemicals which can harm It does not just make rain, the environment especially plants it also regulates water and animals. vapor that in turn prevent damages bought by Since it modifies the weather it destructive hails and might change climatic pattern. storms It saves dry place from It is very expensive. drought Measurement  DISCUSSION OUTLINE 1. Precipitation Gauges 2. The Precipitation Gauge-Network What is the significance of measuring precipitation?  Precipitation Gauges Rain Gauges - used to measure rainfall over an area in a predefined period of time. Methods of converting point rainfall to area rainfall 1. Arithmetic Mean Method 2. Isohyetal Method 3. Thiessen Polygon Method  Types of Rain Gauge 1. Non- Recording Rain Gauge  Types of Rain Gauge 2. Recording Rain Gauge (Tipping Bucket Rain Gauge)  Other measuring instruments 3. Automatic Rain Gauge-observe rainfall amount every 10 minutes and automatically send the data to a collection server at PAGASA in Quezon City.  Other measuring instruments 4. Automatic Weather Station (AWS) -These automated stations have built in weather instruments with electronic sensors for measuring surface level air temperature pressure, solar radiation, rainfall amount, wind speed SMS; the stations have integrated data banks for storage of recorder data for later retrieval.  Other measuring instruments 5. Automatic Aviation Weather Observation System (AWOS) - The AWOS helps pilots and aviation personnel make critical decisions by providing continuous, real-time information and reports on airport weather conditions.  Other measuring instruments 6. Radio Detection and Ranging (RADAR) - A weather surveillance radar (WSR) is useful in locating precipitation and estimate its intensity and in determining the center of tropical cyclones. In addition to this capability, state- of- the-art Doppler radars are capable of estimating radial velocity which can be used to determine the wind strength of tropical cyclones as well as to analyse its structure.  The Precipitation Gauge-Network : is a system of strategically placed instruments designed to measure the amount of rainfall or precipitation in a specific area. PAGASA Automatic RG coordinates Components of Precipitation Gauge-Network 1. Rain Gauges - Instruments that collect and measure the amount of liquid precipitation over time. 2. Data Collection Points - Multiple gauges placed at various locations to capture localized variations in precipitation. 3. Central Monitoring System - A networked system that collects and processes data from all gauges for analysis.  Why are Gauge-Networks Important? 1. Flood Prevention - Accurate precipitation data helps predict potential flooding events 2. Water Resource Management -Helps in planning for reservoirs, irrigation, and drinking water supply. 3. Climate Monitoring -Tracks changes in precipitation patterns over time, aiding climate change studies. INTERPRETATION OF PRECIPITATION DATA INTERPRETATION OF PRECIPITATION DATA ESTIMATING MISSING PRECIPITATION DATA DOUBLE-MASS ANALYSIS AVERAGE PRECIPITATION OVER AREA DEPTH-AREA-DURATION ANALYSIS https://philsensors.asti.dost.gov.ph/ INTERPRETATION OF PRECIPITATION DATA Estimating missing precipitation data Estimating Missing Precipitation Data Many precipitation stations have short breaks in their records because of absences of the observer or because of instrumental failures. It is often necessary to estimate this missing record. Methods of Obtaining Missing Rainfall Data A. ARITHMETIC MEAN METHOD B. NORMAL RATIO (NR) METHOD C. INVERSE DISTANCE WEIGHTING (IDW) METHOD A A G Nadiatul Adilah and H Hannani 2021 IOP Conf. Ser.: Earth Environ. Sci. 682 012027 Estimating Missing Precipitation Data 1. ARITHMETIC MEAN METHOD If the normal annual rainfalls at surrounding gauges are within 10% of the normal annual precipitation at the stations concerned, then the arithmetic procedure could be adopted to estimate the missing data. This assumes equal weights from all nearby rain gauge stations and uses the arithmetic mean of the precipitation data Px = Estimate for the target station (X) Pi = Rainfall values of rain gauges used for estimation m = Number of surrounding stations A A G Nadiatul Adilah and H Hannani 2021 IOP Conf. Ser.: Earth Environ. Sci. 682 012027 Estimating Missing Precipitation Data 2. NORMAL RATIO (NR) METHOD This method is used if the normal annual precipitation of any surrounding gauges exceeds 10% of the gauge that is under consideration. This weighs the effect of each surrounding station. Px = Estimate for the target station (X) Pi = Rainfall values of rain gauges used for estimation m = Number of surrounding stations Nx = Normal annual precipitation of the X station Ni = Normal annual precipitation of the surrounding stations A A G Nadiatul Adilah and H Hannani 2021 IOP Conf. Ser.: Earth Environ. Sci. 682 012027 Estimating Missing Precipitation Data 3. INVERSE DISTANCE WEIGHTING (IDW) METHOD In this method, the weight for each station is assumed to be inversely proportional to its squared distance of the target station from the neighbouring station with data Px = Estimate for the target station (X) Pi = Rainfall values of rain gauges used for estimation m = Number of surrounding stations Di = Distance from each location to the point being estimated A A G Nadiatul Adilah and H Hannani 2021 IOP Conf. Ser.: Earth Environ. Sci. 682 012027 INTERPRETATION OF PRECIPITATION DATA Double-Mass Analysis  Double-Mass Analysis Changes in the location or exposure of a rain gage may have a significant effect on the amount of precipitation it measures, leading to inconsistent data (data of different nature within the same record). The consistency of a rainfall record is tested with double-mass analysis. V. M. Ponce, Engineering Hydrology Principles and Practice, Prentice Hall, 1989.  Double-Mass Analysis This method compares the cumulative annual (or alternatively, seasonal) values of station X with those of a reference station. The reference station is usually the mean of several neighboring stations. The cumulative pairs (double-mass values) are plotted in an xy arithmetic coordinate system and is examined for trend changes. X - Axis = Accumulated Precipitation of Nearby Stations Y - Axis = Accumulated Precipitation of Considered Stations  Double-Mass Analysis If the plot is essentially linear, the record at station X is consistent. If the plot shows a break in slope, the record at station X is inconsistent and should be corrected. The correction is performed by adjusting the records prior to the break to reflect the new state (after the break). To accomplish this, the annual rainfall data prior to the break are multiplied by the ratio of slopes after and before the break. Double-Mass Analysis INTERPRETATION OF PRECIPITATION DATA Average Precipitation Over Area (Estimation of Areal Precipitation)  Average Precipitation Over Area The average depth of precipitation over a specific area, either on a storm, seasonal, or annual basis, is required in many types of hydrologic problems. A single point precipitation measurement is quite often not representative of the volume of precipitation falling over a given catchment area. A dense network of point measurements and/or radar estimates can provide a better representation of the true volume over a given area. Average Precipitation Over Area Methods of Obtaining Aerial Precipitation A. ARITHMETIC MEAN METHOD B. THEISSEN POLYGON METHOD C. ISOHYETAL METHOD  Average Precipitation Over Area 1. ARITHMETIC MEAN METHOD The simplest method of obtaining the average depth is to average arithmetically the gaged amounts in the area. This method yields good estimates in flat country if the gages are uniformly distributed and the individual gage catches do not vary widely from the mean. These limitations can be partially overcome if topographic influences and areal representativity are considered in the selection of gage sites.  Average Precipitation Over Area 1. ARITHMETIC MEAN METHOD  Average Precipitation Over Area 2. THIESSEN POLYGON METHOD This is a graphical technique which calculates station weights based on the relative areas of each measurement station in the Thiessen polygon network. The individual weights are multiplied by the station observation and the values are summed to obtain the areal average precipitation. https://www.weather.gov/abrfc/map  Average Precipitation Over Area 2. THISSEN POLYGON METHOD The results are usually more accurate than those obtained by simple arithmetical averaging. The greatest limitation of the Thiessen method is its inflexibility, a new Thiessen diagram being required every time there is a change in the gage network. Also, the method makes no attempt to allow for orographic influences.  Average Precipitation Over Area 2. THEISSEN POLYGON METHOD Steps in Making Theissen Polygon Network: 1. Draw straight lines connecting 2 stations. 2. Draw a perpendicular bisector between the 2 stations and extend until it meets with another bisector within the area.  Average Precipitation Over Area 2. THIESSEN POLYGON METHOD  Average Precipitation Over Area 2. THIESSEN POLYGON METHOD https://www.weather.gov/abrfc/map  Average Precipitation Over Area 3. ISOHYETAL METHOD This is a graphical technique which involves drawing estimated lines of equal rainfall over an area based on point measurements. The magnitude and extent of the resultant rainfall areas of coverage are then considered versus the area in question in order to estimate the areal precipitation value. https://www.weather.gov/abrfc/map  Average Precipitation Over Area 3. ISOHYETAL METHOD It is considered as the most accurate method of averaging precipitation over an area. Station locations and amounts are plotted on a suitable map, and contours of equal precipitation' (isohyets) are then drawn The average precipitation for an area is computed by weighting the average precipitation between successive isohyets (usually taken as the average of the two isohyetal values) by the area between isohyets, totaling these products, and dividing by the total area.  Average Precipitation Over Area 3. ISOHYETAL METHOD Steps in Isohyetal Analysis Method: 1. Draw lines of equal precipitation. Estimate precipitation in each grid area within basin. 2. Sum the values in each grid area. 3. Divide the sum by the number of grid areas to obtain a basin areal estimate of precipitation. https://www.weather.gov/abrfc/map  Average Precipitation Over Area 3. ISOHYETAL METHOD INTERPRETATION OF PRECIPITATION DATA Depth-Area-Duration (DAD) Analysis  Depth-Area-Duration Analysis Depth-Area-Duration (DAD) analysis is a procedure to determine the maximum amount of rainfall of different durations over a range of areas. Various hydrologic problems require an analysis of time as well as areal distribution of storm precipitation. Basically, depth-area-duration analysis of a storm is performed to determine the maximum amounts of precipitation within various durations over areas of various sizes. Depth-Area-Duration Analysis PMP-DAD Curve for Different Durations in Yongdam-dam Basin. VARIATION IN PRECIPITATION Geographic Variation Time Variation Record Rainfall  Geographic Variation Latitude - Precipitation generally decreases as you move away from the equator towards the poles. This is due to the Earth's curvature and the angle at which sunlight strikes different latitudes. Geographic Variation  Geographic Variation Precipitation and precipitable-water data were extracted for 10-degree latitude points, averaged across longitudes, and analyzed for the years 1948-2009. Latitude Patterns: -Precipitable water decreases smoothly towards the poles. -Precipitation rate exhibits minor peaks around -50° and 50° latitude, with minima around -30° and 30°. According to the study of L. David Roper (6 April, 2016). http://arts.bev.net/roperldavid  Geographic Variation Elevation - Higher elevations often receive more precipitation, especially in mountainous regions. This is due to the cooling effect of rising air as it ascends mountains, leading to condensation and precipitation.  Geographic Variation Proximity to bodies of water - Areas near oceans or large lakes tend to receive more precipitation due to the evaporation of water from these bodies, which forms clouds and leads to precipitation.  Geographic Variation Prevailing winds - The direction and strength of prevailing winds can influence precipitation patterns. For example, wind carrying moist air from oceans can bring precipitation to coastal regions.  Time Variation Seasonal variations - Precipitation can vary significantly throughout the year, depending on factors like monsoon patterns, winter storms, and summer thunderstorms. https://weather-and-climate.com/average-monthly-Rainfall-Temperature- Sunshine,Manila,Philippinesit of body text  Time Variation Daily variations - Precipitation can occur at any time of day, but there may be patterns related to specific weather conditions, such as afternoon thunderstorms or morning fog. Amount of daily rainfall recorded at the Science Garden synoptic station in Quezon City, Philippines (Data reference: National Oceanic and Atmospheric Administration (NOAA), 2021).  Time Variation Long-term trends - Precipitation patterns can change over time due to factors like climate change and natural variability.  Time Variation Precipitation size and speed  Time Variation Precipitation size and speed Source: Lull, H.W., Soil Compaction on Forest and Range Lands, U.S. Dept. of Agriculture, Forestry Service, Misc. Publication No.768  Record Rainfall Extreme events - Occasionally, regions experience extremely heavy rainfall events, which can lead to flooding and other disasters. These events are often associated with specific weather patterns, such as hurricanes or tropical storms. Disaster brought by bagyong Enteng  Record Rainfall Historical records - Records of precipitation can be used to track long-term trends and identify extreme events. These records can provide valuable information for understanding climate variability and planning for future challenges.  SNOW COVER AND SNOWFALL  Measurement How to measure snow fall?  Variations 1. Flurries Light snow showers with minimal accumulation, often short-lived.  Variations 2. Snow Showers Snowfall that occurs irregularly and varies in length and severity.  Variations 3. Snow Squalls Brief, intense bursts of snow, often accompanied by strong winds.  Average Precipitation Over Area 3. ISOHYETAL METHOD https://www.weather.gov/abrfc/map  Variations 4. Snowstorm A prolonged period of snowfall that can be heavy and consistent.  Variations 5. Blizzard Severe snowstorms with strong winds and low visibility.  Variations 6. Sleet (Freezing Rain) Rain that falls and freezes into ice pellets before reaching the ground. SUMMARY