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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 : [email protected]
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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