An overview of

Weather Observation

Practices over Pakistan

Summer School on Managing Shared River Basins: Connecting Science &

Policy for Integrated Water Resources Management” (2-6 July, 2018)

By

Fayyaz Ahmed

Pakistan Meteorological Department

1. AVIATION METEOROLOGICAL SERVICES

2. HYDRO-METEOROLOGICAL SERVICES AND FLOOD FORECASTING

3. AGRO-METEOROLOGICAL SERVICES

4. CLIMATOLOGICAL SERVICES

5. GEOPHYSICAL AND SEISMOLOGICAL SERVICES

6. WEATHER FORECASTING SERVICES TO PUBLIC THROUGH ELECTRONIC & PRINT

NEWS MEDIA

7. ASTRONOMICAL INFORMATION SERVICES

8. MET-FORECAST FOR MOUNTAINEERING EXPEDITION / MARINE

METEOROLOGICAL SERVICES

9. GLACIER MONITORING AND MOUNTAIN HAZARDS

10. FOG SERVICE

SERVICES DELIVERED BY PMD

Observations are key to our understanding of how the the atmosphere shapes our weather and climate.

• Currently, well over 10 000 manned andautomatic surface weather stations

• 1 000 upper-air stations• 7 000 ships• 1 000 drifting buoys• Hundreds of weather radars and 3 000 specially

equipped commercial aircraft measure keyparameters of the atmosphere, land and oceansurface every day.

• Add to these some 16 meteorological and 50research satellites to get an idea of the size of theglobal network for meteorological, hydrologicaland other geophysical observations.

• Once collected, observations are quality-controlled, based on technical standards definedby the WMO Instruments and Methods ofObservation Programme (IMOP), then madefreely available to every country in the worldthrough the WMO Information System (WIS).

Surface observation stationDistribution map of station

Surface observation station

• Surface observation stations

• Pilot Balloon Observation

• Upper air Rawin Sonde Station

• Weather Surveillances Radars

• Vertical wind profiler (SODAR)

• Automatic Weather Station

Number of Surface observing stations over Pakistan

98

35

02

07

01

37

Instruments and Times of Observation

Generally there are two classes of the Meteorological surface observatoriesin PMD:

These observatories are provided with:

• Barometer ( Mercury Aneroid )/self recording instrument

• Maximum Thermometer

• Minimum Thermometer

• Dry Bulb

• Wet Bulb

• Anemometer

• Wind Vane

• Rain Gauge + Measuring glass

• Observing watch

• Stevenson Screen

Class-I observatories take synoptic observations at least eight times daily at thestandard UTC hours i.e. 0000, 0300, 0600, 0900, 1200, 1500, 1800, 2100.

Class-II Observatories:

These observatories are provided with the eye reading equipment only and recorddaily at least three (3) synoptic observations at standard hours 0000, 0300 &1200 UTC.

Some Met. Instruments

Instruments maintenance & calibration

*M- maintenance, C- calibration

S

NElement Instrument Make & Model Current

Status

MaintenanceInterval &

Calibration *

1 Pressure Mercury-filled

Barometer

F. Darton & Co.London 1955

Functional Biannually (M) &Annually (C)

2 Temperature Mercury-filled

Thermometer

G. H. Zeal/ RW MunroLondon 1970

Functional Biannually (M) &Annually (C)

3 Humidity Hair hygrograph Casella/ FairmountLondon, 1980

Functional Biannually (M) &Annually (C)

4 Wind Electrical

Anemometer

PMD, 2010 Functional Biannually (M) &Annually (C)

5 Precipitation Rain gauge (Manual

+Automated)

PMD, 2010 Functional Biannually (M) &Annually (C)

6 Sunshine

duration

Sunshine recorder German, 2005 Functional Biannually (M) &Annually (C)

Manufacturer ,model & current status

Weather observation (visual+instrumental)

Cloud Condition (Amount, Type, Height) Weather Situation (Fog, Thunderstorm) Visibility Temperature (Dry &Wet Bulb, Dew Point ,RH) Wind (Mean Wind, Gust) Rainfall amount (specialized measuring cylinder) Atmospheric Pressure

In addition to these core measurements, grass minimum temperature and soil temperatures sunshine duration, solar radiation and evaporation rate are also recorded

Encoding Weather Information

In a language which is understandable around the world, theweather information are encoded in the form of series of numbercalled SYNOP CODEHere is an example of coded message

41640 21696 42304 10325 20215 39736 49971 70420 82530 333 2031056990 59018 60007 52%=

Which country the observation is from and which weather station 41 means the Pakistan 640 means Lahore 2 Indicator for inclusion or omission of precipitation data 1 Identifies a manned/unmanned weather station 6 means height of lowest cloud base 96 refers minimum visibility using the vv code

96= Object visible at 4000m not at 10,000 m 4 identifies cloud cover in Oktas (eights)

Encoding Weather Information

41640 21696 42304 10325 20215 39736 49971 58012 70520 82530 33320310 56990 59018 60007 52%=

23 show wind direction in tens of degrees 23=230 04= wind speed in knots 1 represent the dry bulb (air) temperature group. 0 Indicates that value is above freezing if 1 than below freezing 325 Air temp in degrees and tenths (temp is +32.5 C) 2 identifies Dew Point Temp group (i.e DP temp = +21.5) 3 identifies station level pressure 4 identifies Mean Sea Level Pressure group

9971 indicates MSL pressure is 997.1 mb 5 identifies the pressure tendency group (Expressed in degrees and

tenths) 7 identifies present and past weather (Haze in present and clouds) 8 Clouds of genera (Amount of individual cloud layer )

National Meteorological Communication Center (NMCC)

• In RTH, the NMCC Karachi is connected with New Delhi through Public Switched Telephone Network(PSTN). There are multiple GTS stations in Pakistan and India. In Pakistan these GTS stationsconnected with NMCC Karachi, This RTH system behaves like a server as well as client whichbroadcast and receive data from India periodically. In the setup of RTH both (NMCC, New Delhi)connected with local telephone exchange. In both end of RTH, the systems connected with localswitch which is further connected with local telephone exchange by which the communication setupis possible.

http://www.pmdnmcc.net/aboutNMCC.aspx

Computerized Data Processing Center(CDPC)

CLIMATOLOGICAL DATA

Types of available Climatological Data are as under:

• Rainfall (mm): 03 hourly, Daily, Monthly, Annual, Heavy Spells in 24Hrs etc.

• Temperature (C): Hourly, Daily, Monthly, Annual, Maximum & Minimum, Extreme Values etc.

• Relative Humidity (%): Hourly, Daily, Monthly

• Surface Wind speed and directions (knots); Hourly, Daily, Monthly

• Sunshine Hours: Hourly, daily

• Station Level/ Mean Sea Level Pressure (hpa) :Hourly, Daily, Monthly

• Amount and types of clouds observed (oktas): Hourly, Daily, Monthly

• Various Weather phenomenon such as, visibility, occurrence of Thunderstorm etc

• Weather Reports on specific weather phenomenon such as heavy rainfall, storm etc

• Windrose diagrams for selected stations.

• Upper-air data (Vertical Profile of the atmosphere) for selected stations

• Agro-meteorological data, such as soil temperature, evapo-transpiration etc., for selected stations.

• Radiation data

• Climate Normals of different parameters (30 years): based on 1931-1960, 1961-1990 and 1971-2000 and 1981-2010 data.

• Daily normals (1981-2010) of temperature and rainfall

• Apart from the above data, there are various other data parameters that can be provided to the individuals according to their demands/requirements

Brief about Global Telecommunication System (GTS)

The functions of the GTS shall be to facilitate the flow of data and processedproducts to meet the WWW requirements in a timely, reliable and cost effectiveway, ensuring that all Members have access to data and products in accordancewith approved procedures and within the limits of the agreed WWW system.

The GTS is an integrated network of surface-based and satellite-basedtelecommunication

GTS links of point-to-point circuits, and multi-point circuits, interconnectingmeteorological telecommunication centres operated by countries for round-the-clock reliable and near-real-time collection and distribution of all meteorologicaland related data, forecasts and alerts.

WMO GTS is the backbone system for global exchange of data and information insupport of multi-hazard, multipurpose early warning systems, including allmeteorological and related data; weather, water and climate analyses andforecasts; tsunami related information and warnings, and seismic parametric

data.

http://www.wmo.int/pages/prog/www/TEM/GTS/index_en.html

The Global Telecommunication System (GTS)

http://www.wmo.int/pages/prog/www/TEM/GTS/index_en.html

The Global Telecommunication System (GTS) is defined as: "The co-ordinated global system of telecommunication facilities and arrangements for the rapid collection, exchange and distribution of observations and processed information within the framework of the World Weather Watch."

Plotting Model

Station Plots

Large amount of meteorological information in small area to build up charts

Synop/Surface Weather chart

Temperature Entropy Diagram

Surface observation stationSurface Observations-Case Examples

•Surface Observatories are mostly manned and at remote areas automated.Problems generally identified are stated below with their possible solutions.

Instrument Troubles/Problems Recovery

Manned

Observatories

•Systematic error whichappears either due to lack ofexperience of observer orinstrumental error.•Procedural Errors in reportingpressure to sea level or misuseof conversion table

•Training of the concernedprofessionals and repair ofinstrument resolve the issues

•Reporting observations insupervision of well trainedprofessional for some time

Automated •Malfunctioning of sensors dueto weathering or pollution•Lack of power due to dustdeposit on solar panel

Regular maintenance in winterand summer seasons ensures thenormal operation of equipment

Instruments in operational useInstruments in Operational Use-Case Examples

•Surface Observatories are mainly equipped with manually operatedinstruments such as thermometers, anemometers, raingauges etc.Instrument Troubles/Problems Recovery

Anemometer •Dust mixed with Lubricantjames/retards the operation•Plastic belt expands/ contractsdue to extreme temperaturesslows meter reading

•Cleaning of mechanical assemblyin kerosene oil/petrol•Change of belt before the onsetof summer and winter wherenecessary in harsh climatic zones

Thermometer • Creation of air bubble• break in column

Both the problems are inter-related and they are recovered byboiling and freezing treatment

Raingauges •Ordinary raingauges collectordevelop some leakage outlet ataged welded points•Self-recording raingauges getclock slow down problems

•Collectors are replaced with acontinuous steel sheet containerand no joint is left•Clock repairs recover the normal

operation