The document discusses agrometeorology, focusing on the relationship between physical environments and agricultural elements, and outlines the objectives of optimizing microclimatic conditions and mitigating agri-business losses due to weather. It details the criteria for selecting agrometeorological stations, recommended instruments for data collection, and the differences between traditional agromet stations and automated weather stations (AWS). The document emphasizes the importance of various meteorological measurements and instrumentation for effective agricultural practices and research.

1. Agrometeorology
2014 Agricultural Engineering Review
Prepared by: Edward R. Lapong, PhD

2. Agrometeorology
- study which deals with the relationship of the
physical environment and agricultural elements
 Physical environment: atmosphere, soil and water
 Agriculture elements: crops and animals
Objective: optimally utilize the existing microclimate
for agricultural purposes;
minimize agri-business losses due to
unfavorable weather conditions;
gather/record data for future studies

3. Agromet stations are usually found in universities
and research institutes/stations, to collect
meteorological and biological data
Major data collected:
- rainfall
- temperature (atmospheric and soil)
- atmospheric pressure
- relative humidity
- wind data
- solar radiation

4. Major data collected:
Phenology – the study of animal and plant life cycle as
affected by seasonal variations of climate
- evaporation
- phenological observations (crop growth and
production data, animal diseases outbreak,
insect population and infestation, etc.)

5. Recommended Time of Data Collection:
 2~3 times daily, from 8 AM~5 or 6 PM
(8am, 10am, 12am, 2am, 4pm, 6pm); (8am, 11am, 2pm, 5pm)
Parameter Standard Agromet Station AWS
Rainfall 24-hr 1-, 5-, 30-min; 1-hr
Solar Radiation 12-, 24-hr 1-hr
Temperature,
Pressure, Humidity
2-, 3-hr 1-hr or less
Wind Speed &
Direction
2-, 3-hr 1-hr or less
Cloud/Sky Condition 2-, 3-hr 1-hr

6. Standard Agromet Station (recommended by PCARRD)

9. Criteria for selection of Agromet Station site:
 Accessibilty for data monitoring, operation
and maintenance
 Should be in a location truly representative
of the natural conditions of the agricultural
region it suppose to serve
 Site has no problem on right of way,
ownership and security
 Site is fairly level and flood-free

10.  Site free from obstruction
 at least 4x the height of the nearest obstruction
(other reference: 8-10 times)
 no shadow casted greater part of the day
 Facing north
(east-west direction
should be identified)
Criteria for selection of Agromet Station site:

11. Criteria for selection of Agromet Station site:
 Site has grass cover and no tall weeds
 Site is not concrete, asphalted, nor made
of crushed stone.
 Security should be provided (fence)

12. Agromet Station Instruments:

13. Agromet Station Instruments:
1. Rainfall-measuring instruments:
a. Standard Rain Gage

14. A = 20 cm (8”)
a
AREA
area
10
1







 H
D
h
d 2
2
4
10
1
4


The actual rainfall depth is magnified 10 times
in the collecting cylinder.

16. b. Tipping Bucket Rain Gage

17. b. Tipping Bucket Rain Gage

20. c. Optical Rain Gage

21. d. Weighing-type Rain Gage
Consists of a storage bin atop a pen recording the changes of
weight on a rotating drum.
Unlike Tipping Bucket, it does not underestimate intense rain.
Contains a device to measure the quantity of chemicals
contained in the locations atmosphere. This is extremely helpful
to study the effects of greenhouse gases.
However, they are more expensive.
e. Acoustic-type Rain Gage

22. Ombrometer – rain gage
Disdrometer – measures drop size distribution and
velocity of precipitation
- distinguish rain, snow, hail, etc
Hydrometeors – precipitation

23. Why are rainfall measurements expressed
in terms of depth and not by volume?
Ans.
‘Depth’ (mm) is the amount of rainfall that would
accumulate on a flat, horizontal and impermeable
surface in a given time (min or hr)
a. It is not feasible to calculate rainfall volume
since areal coverage may be different

24. Why are rainfall measurements expressed
in terms of depth and not by volume?
b. To provide an international standard and uniform
measurement of rainfall. It is more simple,
effective and easier to measure, describe and
compare amount of rainfall in ‘depth’.
 For consistency, simplicity and standardization

25. Agromet Station Instruments:
2. Temperature-measuring instruments:
Maximum-Minimum
Thermometers
Ordinary
Thermometers

26. Maximum Thermometer
When temperature rises, the
expanding mercury is forced
past the constriction but when
the temperature falls the
column of mercury remains in
the tube, thus indicating the
maximum temperature

27. b. Aneroid Barometer
Agromet Station Instruments:
3. Pressure-measuring instruments:
a. Mercury Barometer

28. Aneroid Barometer
It is basically a manometer
with one end exposed to the
atmosphere
It is more sensitive than
aneroid barometer since it
has Vernier scale on it and
has already temperature,
elevation and altitude
corrections.

29. Other differences between aneroid barometer and
mercury barometer?
• Aneroid barometer is more stable
and compact, less fragile; thus, is
easy to transport and take readings.
• The mercury barometer can be
constructed easily, but the aneroid
barometer requires machinery.

30. Why is barometer installed inside rather
than outside the building?
Ans.
a. To prevent effect of wind and solar radiation
b. To prevent effect of outside temperature and
humidity
(However, if the room is not airtight, no significant
difference.)
(Vibration and shock may lead to fluctuation)
(Barometer does not give a true reading if affected
by gusty wind.)

31. Why is barometer installed inside rather
than outside the building?
Ans.
c. To prevent wear and tear.
Note: Barometer should not be placed in an air
conditioned room.
(It may create a pressure differential between the
inside and outside environment)

32. Instrument Shelter (Thermometer Screen)
It shields the instruments
against rain and direct solar
radiation while allowing air
to circulate freely around
them.
To provide a standardized
environment in which to put
or keep the temperature-
and humidity-measuring
instruments.

33. Why should instrument shelter be painted
white?
Ans. To reflect the solar radiation and avoid
absorption of radiation that may affect
the setting/calibration and accuracy of
the instruments placed inside.

34. Agromet Station Instruments:
4. Humidity-measuring instruments:
a. Hygrometer

35. b. Hygrothermograph

36. c. Psychrometer
Sling Psychrometer
Hand-held Digital
Psychrometer

37. Dry-Bulb
Thermometer
Wet-Bulb
Thermometer

38. Agromet Station Instruments:
5. Wind-measuring instruments:
a. Anemometer

39. b. Wind Vane

40. Anemometer installation
requirements:
 Site where wind flow freely and
not distracted by obstructions (trees, tall buildings, other
structures)
 Oriented in the prevailing wind direction
 Mast should be absolutely vertical.
2 m – flat urban terrain
4~10 m – for rural terrain
for roof installation: 3 m from the most exposed part
 3-cup

41. Wind vane installation requirements:
 Should be mounted towards true north
(use magnetic compass and corrected by the magnetic
delineation for specific area)
 Satisfactorily exposed and can rotate 3600
 Best mounted in an open terrain, at least 30 m from the
nearest obstruction
(wind can blow freely, no nearby obstruction)
 Mounted 6-10 m above the ground

42. Wind vane installation requirements:
 Could be as simple as
handcrafted wooden or light
metal; or as elaborate with
decorative ornament
 Lightning rod may be installed to
minimize risk of damage during
thunderstorm.

43. Agromet Station Instruments:
6. Evaporation-measuring instruments:
Evaporation Pan

44. Class A Evaporation Pan
120 cm (47.5’) 25 cm
(10’)
Stilling Well
 Class A Evaporation Pan measurement is highly correlated
with the potential evapotranspiration of the surrounding area.

45. Class A Evaporation Pan installation requirements:
 Galvanized iron Gage 20
 Operating water level depth: 175~200 mm
(water level kept at 50~75 mm from the rim)
 Installed 150-mm from the ground on wooden
stand/platform
 Measuring stick is 1.0 m and accuracy of 0.02 mm.

46.  Measurement should be done in still well as it
prevents the effect of waves and ripples which
affects accuracy.
Why should measurement be done in the
stilling well?

47. Agromet Station Instruments:
6. Solar Radiation-measuring instruments:
a. Sunshine Recorder

48. Campbell-Stokes
Sunshine Recorder:
A device that measures or
records the amount of
sunshine at a given location.
Campbell-Stokes
Sunshine Recorder

49. b. Actinometer – used to measure heating power of radiation
Solar radiation as transmitted directly by the sun,
scattered by the atmosphere, or reflected by the earth.

50. c. Pyranometer
A type of actinometer used to
measure broadband solar
irradiance (short wave radiation)

51. c. Pyrheliometer
Used to measure intensity of
direct solar radiation

52. Agromet Station Instruments:
7. Other instruments:
a. Ceilometer
A device which uses a laser
or other light source to
determine the height of
a cloud base.

54. b. Radiosonde
A group of instruments for
simultaneous
measurement and radio
transmission of
meteorological data:
temperature, pressure,
and humidity of the
atmosphere. The
instrument package is
usually carried into the
atmosphere by a balloon.

55.  A typical AWS comprises 8
sensors for measuring wind
speed, wind direction, air
temperature, RH, solar
radiation, soil temp., surface
wetness, and rainfall.
AWS (Automatic Weather Station)
 Battery- or solar-powered.

56. What are the differences between a typical
Agromet station and AWS?
 AWS is an automated version of the traditional Agromet
station, either to save human labor or to enable
measurements from remote areas.
 An AWS is equipped with data storage system, thus
data downloading can be done on a daily, weekly, or
monthly basis. The frequency of data collection can
also be programmed according to the needs and use of
such information.

57.  Moreover, a telemetry system could be connected to
the AWS so that data can be remotely accessed through
mobile SMS or other form of messages in real time.
Thus, data from the AWS can be transmitted in real
time to a central server which can be viewed from
a web-based system through the Internet.
 While, the data from the existing agromet station are
recorded daily in a prescribed form from PAGASA by an
assigned agromet observer and are submitted to BSWM
every month through mail.

59. Data Logger
Rain Gage
Anemometer
Solar
Radiation
Humidity
Solar Panel

60. End