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CHALLENGES POSED BY THE AUTOMATED INDIAN SURFACE OBSERVATIONAL NETWORK AND RESPONSIBILITIES OF REGIONAL INSTRUMENTS MAINTENANCE

CENTRES IN EFFECTIVE QUALITY ASSURANCE

B. Amudha

India Meteorological Department

Regional Meteorological Centre, Chennai, India

Tel.:91-44-282320091/92/94 Fax.91-44-28252002

e-mail : amudha_aug@yahoo.com

ABSTRACT

Diverse challenges in obtaining high quality, reliable data from the automated surface

meteorological network of 675 Automatic Weather Stations(AWS) installed by India Meteorological

Department(IMD) have been discussed. Proportionate contributions are due to topography,

siting, exposure, adversities in weather due to seasonal cycles, tropical storms, environmental

degradation of AWS enclosures, cabling, malfunctioning sensors, clogged rain gauges, pollution

effects on radiation shields, oxidation on connectors, battery leakages, vegetative growth, theft,

problems due to birds and rodents, etc. Some are unique in the Indian scenario and

unpredictable. Regular monitoring and periodic preventive maintenance ensure reliable data. The

need for evolving a standardised methodology for maintenance of log and meta data about the

sites on par with developed countries is highlighted. The importance of the creation of a three-tier

maintenance hierarchy by IMD with centres at the Regional, State and Field level to ensure

maintenance of the vast network is emphasized. The hierarchy is in accordance with the region

wise administrative classification followed by IMD for effective fulfilment of the mandate of

providing weather services.

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1. Introduction India is the seventh largest country in the world with 28 States and 7 Union Territories. The

Bay of Bengal and Arabian Sea form the coastal boundaries on the eastern and western sides.

The Himalayan mountain range extends along the northeastern side with a stretch of land area

on the southwestern side. Each state is unique in terms of topography and maritime influences.

The area of many of the states is larger than some countries in the world. The states have been

divided into 643 districts for administrative purposes. India Meteorological Department (IMD), the

national weather service of the country since the year 1875 has 559 conventional manned surface

observatories. Many more districts are still meteorologically unrepresented. Since the years 2007

to 2012, IMD has augmented the surface observational network by installing around 675

unmanned satellite-based Automatic Weather Stations (AWS) from which hourly meteorological

data is received in near-real time. Among these, 125 were installed during 2007 and the rest

during 2010-12. For the first time in IMD, automation has been introduced to obtain parameters of

agricultural interest as well and 127 AgroAWS in the Agroclimatic Zones of India have been

inducted into the network (Ranalkar et al, 2010). The modernisation initiative of IMD aims at

installation of at least 2000 AWS and 4000 ARGs all over India in a phased manner in the next

five years so as to ensure optimal representation from all districts.

An AWS is ideally located in a site of dimensions 15 m x 12 m and the mast is of 10 m

height. AWS has sensors for measurement of air temperature, relative humidity, wind speed, wind

direction, atmospheric pressure and rainfall. The sensors are mounted in the mast as per the

guidelines stipulated by the World Meteorological Organisation(WMO). AgroAWS have sensors

for measurement of global radiation, soil moisture, soil temperature, leaf temperature and leaf

wetness. Now, the aim of having at least one AWS in each district in the first phase of

modernization is almost achieved barring some districts which have inhospitable terrain. More

AWS will be inducted in the next phase to have spatially dense meteorological representativeness.

Work of installation of 1350 Automatic Rain Gauge (ARG) stations is expected to be completed by

the end of year 2012. All ARGs have rainfall sensor but one third of the network has air

temperature and humidity sensors also at crucial locations. An ARG is located in a site of

dimensions 7 m x 5 m and the mast is of 2.5 m height. Mesoscale ARG networks in few of the

metropolitan cities like Chennai and Delhi capture rainfall and temperature variabilities caused due

to rapid urbanisation and industrialisation.

When the network density is rapidly increasing, the most challenging aspect is the

maintenance of the equipments to obtain data of good quality. Periodic site visits are required at

least on a quarterly basis to obtain reliable and accurate data from the remote AWS and ARGs.

However, due to various limitations, it has not been possible to ensure such a regularity. AWS

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networks are commonplace (Brown and Hubbard, 2001) in developed countries since early

1980s. Such state-of-art unmanned AWS network of IMD has become a reality in India recently.

So, the challenges in this technology are new for the tropical country which experiences four

seasons annually. Standardisation of the maintenance procedures as per WMO guidelines based

on the valuable experience of officials has commenced. Systematic archival of the site conditions

after every visit is crucial to understand the long term variabilities in the exposure conditions of

sites which are susceptible to change due to urbanisation. The usefulness of creating a data base

with meta data of all sites and accessing it through a web based application has been documented

by researchers (WMO, 2010). Archival of digital photographs of the conditions in sites provides

vital information about sites. Quantification of height of the vegetative growth in sites by installing

vegetation height gauges etc. (Feibrich et al, 2006) is important to know the micro-climatic

influences on measurement of weather parameters in such sites.

The objective of this paper is to highlight and bring an awareness about some of the

challenges faced by IMD officials in India while undertaking preventive maintenance of the AWS.

Some technical problems are universal for AWS located all over India while few are region specific

and confined to specific sectors of the country. The concept of creation of a three-tier maintenance

hierarchy by IMD as a visionary initiative to cater to the maintenance of AWS / ARG sites and

other equipments used for meteorological purposes is discussed and its functionalities are dealt

with, though the concept is still evolving. The need for documentation of uniform procedures on

par with countries having similar and larger AWS networks is emphasised.

2. Maintenance requirements

The mammoth task of installation and commissioning of AWS and ARGs in the

entire length and breadth of India is a challenge in itself. Fig.1 is the AWS network (Ranalkar et

al, 2010) installed during 2010-12. The responsibility of ensuring the accuracy and reliability of

data from AWS and ARGs is equally a daunting reality. Maintenance of a network of automatic

stations is often a grossly underestimated task (WMO No.8, 2008). The problems in network

management are universal for all meteorological services in the world. Preventive maintenance of

AWS is the only effective solution for reliable data (Brown and Hubbard, 2001). The value of

routine visits to manage the network and maintain data quality from such AWS networks in

Oklahama has been documented by Fiebrich et al (2006). Apart from the scheduled visits,

sometimes one has to visit the sites on emergency basis to rectify problems in sensors or replace

them on priority so that data gaps are avoided. Faulty or malfunctioning sensors in a site, if left

unattended without replacement or rectification may generate errors in the data collected and

archived which will exceed the tolerance limits and distort results thereby providing wrong

information to the users.

Timely preventive maintenance and ensuring minimum down-time of an AWS or ARG is

the principal task before the meteorologists of IMD. Operational forecasters have done validation

studies and are convinced that AWS data from IMD network yields promising results for its utility in

monitoring and nowcasting of severe weather events (Ajit Tyagi et al, 2010). Data from AWS has

clearly demonstrated compliance with the functional requirements for operational practices but a

number of relevant issues remain to be solved to give AWS an equal status as a manned station.

Complete switch-over and dependability on AWS is possible when maintenance of AWS is given

top priority. Recurring financial expenditure is unavoidable for maintenance and to have a steady

supply chain of spares for replacement of defective ones. Theft and vandalism are also major

challenges to be foreseen prior to installation / selection of a site. Calibration of sensors is another

key area for accuracy and dependability of the data. The cooperation from officials in the sites in

whose premises the AWS is installed is also crucial. Safety of equipments and general upkeep of

the AWS can be taken care of by such volunteers at AWS sites who provide valuable land in their

premises for installation of AWS. They can also assist in visual inspections of the sensors, periodic

cleaning of solar panel and radiation shields of temperature humidity sensors.

Bay of BengalArabian Sea

IMD Network of AWS and Agro AWS

Fig.1. IMD network of AWS and Agro AWS installed during 2010-12

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3. Inspection and cleaning

Efforts are taken to follow a systematic quarterly maintenance schedule. However, at

present sites are visited only once in six months. After visiting a site, the first job is to ensure that

the site is clean, free from bushes and creepers which grow densely in the intervening period

between two site visits. Digital photographs of the site conditions before and after the maintenance

work is taken. Photographs of the condition of other AWS equipments are also taken so that they

will act as guidance for the next team which would visit the site for upkeep. Since IMD AWS are

battery operated and charged by solar panels, a schedule of replacing the battery with a new one,

at least once in two years is followed for uninterrupted and optimum functionality. The fencing,

gate and mast are painted once in a year. The NEMA enclosure is also painted as they get rusted

due to corrosion. All the connectors are tightened which might have expanded due to thermal

expansion. The solar panel, all connectors and their oxidised parts are cleaned. The temperature

and humidity sensor and the radiation- shield housing it are cleaned to make it free from dust

deposits, mud housings made by wasps, webs by spiders and other insects. The filter cap of the

sensor bears the brunt of pollutants and high levels of suspended particulate matter in some

locations and requires cleaning and replacement frequently. The tipping bucket rain gauge(TBRG)

is cleaned and checked by pouring the known quantity of water required for one tilt as per the

resolution of the TBRG. Sometimes creepers and leaves clog the TBRG and rainfall data obtained

from such stations are erroneous which is known only after a visit to the site. Data validation of the

outputs from atmospheric pressure, air temperature and humidity is done by comparing the data

with portable hand-held digital standards carried to the sites by maintenance personnel. In case of

marked deviation in values reported by the sensors, replacement is done and the defective one is

brought back to the laboratory for analysing the cause of the problem. Major type of

troubleshooting is not attempted at sites.

4. Problems experienced during maintenance of AWS/ARG

The problems associated with AWS enclosures, connectors, rain gauges, radiation

shields, cabling, birds and rodents, theft, growth of weeds etc have been discussed

4.1 AWS Enclosures

NEMA enclosures are used to house the data logger, transmitter, battery, pressure sensor

and other control circuitry. MIL-STD connectors for the meteorological sensor cables are preferred

for all weather conditions and rugged use. NEMA enclosure used at present is metallic and

maximum rusting has been observed in the Indian weather scenario, as shown in Fig.2 in coastal

locations where the maritime air loaded with hygroscopic particles causes deterioration of the

NEMA box. The ambient temperature inside the metallic NEMA enclosure increases during hot

weather season, more so when the air temperatures are of the order of 45 to 47 degrees Celsius in

some AWS sites. An instance of an AWS site experiencing extreme hot weather conditions during

the summer months of May showed that the battery had bulged (Fig.3) causing the station to stop

transmitting. Due to bulging and spilling of acid inside the enclosure, the MIL-STD connectors had

got corroded and damaged (Fig.4) resulting in the damage of the connectors including that of wind

sensor. This in turn had resulted in erroneous reporting of wind values. The reason for the non-

functionality of the AWS was not known till preventive maintenance to the site was undertaken.

There is an urgent need for switchover to non-metallic enclosures which can withstand high

temperatures and retain the correct ambient temperature inside the housing of the data logger. In

spite of the fact that gaskets are provided for airtight environment in the NEMA enclosure to avoid

water seepage, during extremely heavy rainfall spells, rainwater seeps inside occasionally thereby

damaging the transmitter / data logger.

 

Fig.2. Corrosion in NEMA enclosure

Fig.3. Spillage of acid from battery under high

environmental temperatures

Fig.4. Damage to connectors due to acid spillage inside NEMA

enclosure

 Fig.5. Oxidation and corrosion in connectors

4.2 Connectors The MIL-STD connectors which are exposed to the vagaries of extremities in weather all

through the year are prone to oxidation and corrosion as shown in Fig.5. After a heavy spell of

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rain, instances have come to notice when water seeps into the minute space between the

connectors resulting in erroneous reporting of data. In southern peninsular Indian region, we have

ensured protection of the MIL-STD connectors by sealing with waterproof tapes and then enclosing

them in flexible transparent plastic pipes as a preliminary measure. More refined methods need to

be thought of. The design of the NEMA enclosure needs to be modified to accommodate the

connectors and cables in such a way as to ensure minimum exposure to the environment and at

the same time facilitating easy troubleshooting and replacement.

4.3 Vegetative growth When an AWS site is left unattended for six months, grass, creepers and bushes grow up to a

height of more than two feet thereby resulting in total blocking of the rain gauge(Fig.6) from

reporting rainfall accurately. A small plant which had grown near the TBRG acted as an umbrella

and covered the collecting area resulting in reduced rainfall value reported by AWS at Puducherry

during tropical cyclone Nisha of the year 2008. Possibility of a bias in reporting of temperature and

humidity values exists when the vegetation is dense. The shrubs and bushes need to be removed

along with the roots while cleaning the site. Spraying weedicides also helps to a certain extent.

Regular upkeep of the AWS enclosure by clearing off the bushes and creepers is a must for

reliable data. A well-maintained AWS site is shown in Fig.7.

Fig.6. Rain gauge covered by

growth of grass Fig.7. A well-maintained AWS site

4.4 Rain gauges

Accurate and reliable rainfall measurements from AWS are possible only with properly

calibrated sensors. Maintenance visits especially prior to the onset of monsoon are a must. Ant-

hills block the free flow of rain water draining out of the rain gauge after recording a pulse. The

TBRG cable is cut or shredded by rodents and needs frequent checks and replacement in case of

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such an eventuality. Reed switches in TBRGs are susceptible to damage due to lightning.

Clogging of the buckets and drain cups of TBRG as shown in Fig.8 occurs due to fine mud brought

by the blowing wind. Bird droppings, dried leaves and twigs which fall into the collector further lead

to wrong readings. Northeastern parts of the country experience intense lightning and heavy

rainfall activity in short durations in the mountainous terrains. To avoid inherent losses due to

missing of pulses in TBRG, heavy intensity gauges are required to withstand and record such

rainfall occurrences. Uniform type of TBRG for all parts of the country is not recommended

according to the experience gained in the few years since automation was adopted.

  

Fig. 8. Clogged bucket and drain cups of the TBRG

4.5 Radiation shields

Conventionally wooden Stevenson screens are used to mount the thermometers which

measure ambient air temperature. In AWS, thermoplastic radiation shields have replaced the

wooden screens. Multiplate radiation shields, without a fan to augment air flow, are used to protect

air temperature sensors when power consumption is a constraint (Richardson and Brock, 1999).

In the Indian context, during winter and summer days on occasions of extreme temperatures (both

lower and higher ranges), errors are induced in measurement of air temperature. Need for an

effective radiation shield suiting local climatological conditions, mainly for the tropical weather

conditions like India where temperatures range from as low as +2 °C to 48 °C in different seasons

requires to be examined. It is felt that use of aspirated shields is also not a viable solution for AWS

under all seasonal conditions considering the limitations in power consumption in a remote AWS.

(Amudha et al, 2008). The slower response of the radiation shield in attaining the ambient

temperature during occasions of heavy rain when moisture over the shield fails to dry up till sun

rise is another feature observed. Wasp-mud houses totally covering the probe is shown in Fig.9.

Spider webs, pollutants and mud blocking the filter of the temperature and humidity probe is shown

in Fig.10. Accumulation of fine mud in between the plates of the radiation shield (Fig.11) vitiate the

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measurements of temperature and humidity and cause large errors. Anti-insect spray will help to

get rid of wasp houses to a certain extent but sometimes the sensors become defective beyond

repair. Frequent preventive maintenance visits and regular cleaning of the plates of the radiation

shield ensures accurate temperature and humidity data.

    

Fig.9. Mud house of wasp in between the plates of the

radiation shield

Fig.10. Spider webs, pollutants and mud deposited on the

temperature and humidity probe

Fig.11. Accumulation of fine mud in the plates of the

radiation shields

4.6 Cabling and other woes

Excess length of the cables of sensors, if wound and kept invite the attention of insects.

Honeycombs (Fig.12) in the cabling cause inconvenience to the maintenance personnel.

Movement of reptiles in areas of thick vegetative growth is inevitable. The skin shed by a snake is

visible in the antenna boom of the mast (Fig.13). Snails in an AWS site close to the sea sneak

into cosy corners of the AWS equipment(Fig.14) which cause lot of trouble and painstaking work

in cleaning the sites.

Fig.12. Honeycomb in cabling Fig.13. Skin shed on the Fig.14. Snails on the angle

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antenna boom by a snake indicator of a planar antenna Routing of the cables of wind sensor, antenna, solar panel and other sensors is done along

the body of the 10m mast. The cables are tied with the help of cable ties. It has been observed

that due to hot weather and continuous exposure the cable ties become brittle and fall down to the

earth, resulting in the dangling of the cables in mid-air. Whenever wind speeds are high the cables

are corroded due to contact with the body of the mast and get damaged due to such constant

oscillations. This problem has resulted in damage of the cable of the wind sensor in particular and

wind values of 80 – 90 knots in fair weather conditions have been reported which indicated open

circuit values. Sometimes, birds perching on the mast damage the transducers of the ultrasonic

wind sensor by poking with their beak. Occasions when birds build their nest in between the N-S /

E-W transducers of the ultrasonic wind sensor have also come to notice which result in erroneous

reporting of wind.

Further, touring officials climb the 10 m mast to check the wind sensor atop the mast,

cables, transmitting antenna, clean the solar panel, and to paint the mast under unsafe conditions.

Providing safety belts to them does not solve the problem as some officials feel that it is uneasy

and constrains movement. Better professional ways have to evolve in compliance with the

regulations of the Indian legislation on Occupational Safety and Health. An effective solution for

the future installations would be to have collapsible / frangible masts like those used in airport

runways so that maintenance of the wind sensor can be done with ease.

4.7 Theft and vandalism

Unforeseen theft of equipments like battery, solar panel and other components of an AWS

and vandalism lead to non-functional status of an AWS and hence loss of data. Siting and

exposure of AWS sites are very important and ideal sites are not always available. Real world is

not perfect and compromises are necessary (WMO, 2010). Certain regions are more prone to

such frequent thefts and hence alternate sites are being considered so that AWS can be relocated.

Data gaps are unavoidable and this is also another contentious issue as cost-factor is involved.

4.8 Creating awareness and capacity building

Considering the vast aerial extent of India, it is not always possible for officials from a

Regional Centre to visit the site due to distance and cost incurred for travel etc. A viable and

practical solution would be to identify technically competent officials from existing IMD

observatories in the vicinity of AWS and impart proper training to them . They can keep a watch

on the performance of AWS near to their observatory and ensure that the general upkeep and

maintenance are done more frequently rather than once in six months. Availability of adequate

spare sensors to immediately replace defective ones is an important necessity. Awareness among

the general public needs to be inculcated as part of the implementation of the project of

commissioning AWS with special reference to Indian conditions considering the different strata of

society. Human resources need to be tapped to the full potential and coupled with good training

the vast network of AWS and ARGs can be effectively maintained by taking into account the

challenges ahead for IMD in maintenance and quality assurance of the data from the automated

network.

5. Creation of a three-tier maintenance hierarchy

The vast automated network which is on the threshold of a new beginning in the history of

IMD with scope for future expansion on a larger scale needs to be effectively managed to obtain

best quality data on par with global standards. The formal procedures prescribed by the

International Organization for Standardization (ISO) for quality management and quality assurance

are also appropriate for meteorological data. The WMO Quality Management Framework (WMO,

2005a) gives the basic recommendations. WMO guidelines help the National Meteorological and

Hydrological Services (NMHS) all over the world to strive for constant improvement in providing

efficient public weather services. A methodical approach with documentation about the procedures

for maintenance, especially keeping records of everything that has been found defective and how it

was rectified etc., helps in quality assurance of the data.

Fig.15. Three-tier maintenance hierarchy Fig.16. Six Regional Meteorological Centres of

IMD

Regional Instruments Maintenance Centre (RIMC)

State Instruments Maintenance Centre (SIMC)

Field Maintenance Unit (FMU)

With an aim of implementing the quality assurance procedures laid down by the WMO, the

concept of creation of a three-tier maintenance hierarchy with Regional Instruments Maintenance

Centres (RIMCs), State Instruments Maintenance Centres (SIMCS) and Field Maintenance Units

(FMU) at IMD sub-offices is emerging (Fig.15) and will immensely help in effective maintenance of

AWS and ARGs. Six regionwise classifications (Fig.16) of the country have been made by IMD for 11

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administrative reasons and are called the Regional Meteorological Centres (RMC). Every RMC will

have an RIMC which will coordinate with SIMCs and FMUs. Each RMC has a few States under its

jurisdiction and each State in general (barring a few exceptions) has a Meteorological Centre (MC)

to cater to the local weather forecasting services to be rendered by IMD. These MCs are

designated as SIMCs. Since each state comprises of many districts, a group of four to five districts

according to their location in the vicinity of a nearby meteorological observatory of IMD is brought

under such an observatory designated as FMU.

5.1 Role of RIMCs RIMC will serve as the nodal office in a region which will coordinate with the respective

Instruments Headquarters(IH) at Pune and Delhi for all types of equipments for technical support,

network management, planning preventive maintenance tours and seeking supply of spares. The

policy decisions of the headquarters will be implemented through RIMCs. RIMCs will coordinate

with SIMCs and FMUs to ensure that the network performance is optimal and non-functional ones

are revived within the minimum possible downtime. RIMCs will ensure that FMUs undertake

maintenance tours. RIMCs will broadly have the following responsibilities though the list can be

endless as the role of RIMCs is wider to provide the impetus and leadership in data quality

management. to SIMCs and FMUs.

i) Liasion with the firms who take care of the equipments during warranty period.

ii) Coordinate with and assist SIMCs and FMUs for preventive maintenance and rectification

of faults at sites after warranty period when the sites come under IMD’s purview.

iii) Undertake tours when SIMCs and FMUs are unable to solve problematic issues

iv) Monitor the data quality

v) Validate with ground truth

vi) Impart training to personnel and develop technical expertise

vii) Plan and ensure availability of spares by placing the annual requirements to the

headquarters

viii) Calibrate the sensors periodically

ix) Take proactive measures to avoid data gap

x) Select sites for network expansion

xi) Liasion with departments who provide sites for AWS / ARG installations

xii) Maintain meta data of sites.

xiii) Conceive and design a web based application for the network maintenance aspects

xiv) Ensure that sufficient tool kits and spares are available with SIMCs / FMUs

xv) Seek technical guidance from the headquarters if faults are beyond rectification at the

level of RIMCs.

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5.2 Role of SIMCs

The prime role of SIMCs is to ensure data quality by undertaking periodic site visits for

maintenance of AWS and ARGs in their vicinity. Apart from assisting the RIMCs in network

management, SIMCs are required to monitor the status of all equipments in their state, maintain

records of the equipments under its control, guide and assist FMUs in fault rectification, have

sufficient stock of spares for providing to FMUs, seek suggestions and provide updates to RIMCs

about their requirements. SIMCs will provide financial support for tours and contingent expenses of

FMUs in consultation with RIMCs. SIMCs will also have a designated group of districts for which

maintenance has to be done.

5.3 Role of FMUs

FMUs will coordinate with SIMCs and take care of the basic maintenance aspects like the

general upkeep of a site by ensuring that the vegetative growth is kept at the optimum height.

Trained manpower from the FMUs will visit the site at least once in a month to clean the rain

gauge, solar panel, check the battery voltage, cables for any physical damage, visually check the

sensors for any fault and if spares are available with them they will replace the defective ones.

More responsibilities will be assigned to FMUs after review of the success of the plan proposed.

6. Summary

Various challenges in maintaining a vast network of AWS and ARGs which are unique in

the Indian context have been brought out. Regular upkeep of the AWS enclosure by clearing off

the bushes and creepers is a must for reliable data. Accurate and reliable measurements from

AWS are primarily possible with proper calibration of sensors and periodic maintenance schedule.

Errors which are induced due to environmental factors indicate the importance of frequent visits to

sites for visual inspection and cleaning. Theft of equipments like battery, solar panel and other

components of an AWS and vandalism leads to non-functional status of an AWS and hence loss

of data. Awareness among the general public about the valuable nature of weather data needs to

be inculcated inculcated as part of the existing network management and in future implementation

of the project of commissioning more AWS. Most developed countries having AWS in their

network have already made efforts to overcome such challenges. IMD has commenced efforts to

standardize the maintenance procedures as per WMO standards is inevitable in the changing

technological scenario. The implementation of the three tier hierarchy for maintenance will help in

better network management and assurance of better data quality for use by the forecasters.

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Acknowledgement

The author thanks the Dy.Director General of Meteorology, Regional Meteorological

Centre, Chennai for his encouragement and support. Inputs and suggestions from the RIMCs at

other regions of India and the team members of RIMC at Chennai are gratefully acknowledged.

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