U.S. DEPARTMENT OF COMMERCENational Oceanic and Atmospheric Administration
NATIONAL WEATHER SERVICE
Silver Spring, Md. 20910
U.S. DEPARTMENT OF COMMERCEJuly 5, l984 W/OM14
TO: All Holders of Operations Manual
SUBJECT: Transmittal Memorandum for Operations Manual Issuance 84-9
1. Material Transmitted:
WSOM Chapter B-18, "Agricultural Weather Stations."
2. Summary:
This chapter describes the types of special observing stations used in the agricultural weather service and discusses program management, instrumentation, forms, and other related matters.
Revisions in this chapter include the following:
a. Addition of new types of instrumentation now available.
b. Discussion of automated observations, using microprocessors.
c. Elimination of the obsolete 3-page WS Form B-57.
d. Addition of the fruit frost observing program.
3. Effect on Other Instructions:
Cancels WSOM Chapter B-18, Transmittal Issuance 75-27, dated December 17, 1975.
Richard E. Hallgren
Assistant Administrator
for Weather Services
Issue Date Org. Code NATIONAL WEATHER SERVICE Part Chap.
7-5-84 W/OM14 Operations Manual B 18
AGRICULTURAL WEATHER STATIONS
Table of Contents:
1. Purpose
2.1 Agricultural Weather Observing Stations (AWOS)
2.2 Micrometeorological Observing Stations (MMOS)
2.3 Fruit Frost Observing Stations (FFOS)
5. Forms
5.1 WS Form B-43
5.2 AWOS's
5.3 MMOS's
5.4 FFOS's
Exhibits:
* * * * *
1. Purpose. This chapter describes the types of special observing stations used in the agricultural weather service and discusses program management, instrumentation, forms, and other related matters.
2. Types of and Requirements for Observing Stations. This section describes the types of and requirements for observing stations used in the agricultural program.
2.1 Agricultural Weather Observing Stations (AWOS). Observations from AWOS's are needed for preparing meteorological forecasts in agricultural areas. They also used for official publication, disease and pest management activities, crop operations status reports, soil moisture analyses, hydrology, and climatology. Sites for AWOS's are selected where observations will be representative of the adjacent agricultural environs. Instrumentation of AWOS's is described in subsection 4.1.
2.2 Micrometeorological Observing Stations (MMOS). The more detailed measurements available from MMOS's are required for research in agricultural weather relationships, as well as for publication, disease and pest management activities, plant and operations models, hydrology, and climatology. MMOS's are usually located at agricultural research stations. Sites are selected where the observations are representative of conditions experienced by the crops in the immediate vicinity of the observing sites. Instrumentation is described in subsection 4.2.
2.3 Fruit Frost Observing Stations (FFOS). FFOS data are used for the issuance of frost forecasts, for research, and to monitor factors such as the number of hours the temperature is below a given threshold value. Instrumentation is described in subsection 4.3.
3. Program Management. The requirement for the three types of observing stations varies considerably across the United States, as does the organizational structure of the agricultural weather service. Therefore, each National Weather service (NWS) region, in cooperation with appropriate field offices, is responsible for determining under what circumstances and how observing stations will be established or eliminated. The Cooperative Program Manager (CPM) may play an active role in the day-to-day management of the program; this will depend on regional policy. Where playing an active role, the CPM would be responsible for determining the representativeness of the site and for providing the necessary instrumentation.
When establishing agricultural weather stations which are a part of the Cooperative Program Network, the responsible NWS office or CPM will complete WS Form B-43, Request for Establishment or Change in Status of Station. A sample of WS Form B-43, reduced in size, is shown as exhibit B-18-1. See subsection 5.1 for instructions on completing this form. The CPM will also complete any additional forms required to establish the station. All forms are then sent through regionally designated channels to the Data Acquisition Division of the appropriate NWS regional office.
4. Instrumentation. This section describes the required and optional meteorological instrumentation for each type of station.
a. Required Instrumentation:
(1) Either a Cotton Region Shelter with a maximum and minimum thermometer or a Maximum-Minimum Thermometer System (MMTS).
(2) Standard (8 inch) rain gage (top horizontal).
(3) Soil thermometer - Palmer or recording type, in soil 4 inches under bare ground.
b. Optional Instrumentation:
(1) Hygrothermograph.
(2) Evaporation set for measuring amount and rate (see NWS Observing Handbook No. 2). Automatic evaporation measuring systems may be substituted if available. Equipment should be the same as or equivalent in capabilities to the following:
(a) Pan, monel metal.
(b) Stilling well, point gage, and measuring tube. Comparable electronic equipment may be substituted.
(c) Anemometer, totalizing or recording.
(d) Six's thermometer or comparable type.
(3) Wind direction and speed recording system elevations above ground may vary from 20 to 33 feet.
(4) Recording (weighing) rain gage (top horizontal)
(5) Davis-Hughes vegetative wetting recording system including Esterline-Angus (or similar type) 0-1 milliampere recorder. (Seven sensors in parallel mounted in and over the canopy of a broad-leaf evergreen 2-4 feet in height with sensors mounted at various heights and degrees of shading -- single sensor used occasionally).
(6) Solar radiation sensor.
4.2 MMOS's. Listed below are the required and optional instruments for a MMOS. World Meteorological Organization standards will be followed in all meteorological parameters measured by the MMOS's.
a. Required Instrumentation:
(1) Cotton Region Shelter with maximum and minimum thermometers or MMTS. The bottom of the shelter should be 4 feet above the ground with thermometers 5 feet above.
(2) Standard 8 inch rain gage (top horizontal).
(3) Recording rain gage (top horizontal).
(4) Pyranometer (Eppley or comparable type).
(5) Soil thermometers -- Palmer or recording type, in soil 4 inches under bare ground.
(6) Minimum thermometer or thermistor, shielded from the sun's rays and mounted 2 inches above a grass surface.
(7) Evaporation [see subsection 4.1.b.(2)]
b. Optional Instrumentation:
(1) Soil thermometer sensors located at 8, 20, and 40, and occasionally at 80-inch depths, under both bare soil and short sod if feasible. Yellow Springs Thermolinear type sensors may be used.
(2) Soil moisture meters such as continuously recording monel, fiberglass, or gypsum resistance blocks. Volumetric soil moisture averages for 8 inch and 5 foot depths.
(3) Net Radiometer with recorder.
(4) Ozone meter with recorder.
(5) Vegetative wetting recording system [see subsection 4.1.b.(5)].
(6) Dew-point/dry-bulb temperature measuring system (Yellow Springs lithium chloride type of sensor for dew point). Sensors are mounted 5 feet above the ground.
(7) Wind direction and speed recording system -- elevations above ground may vary from 10 to 33 feet.
(8) Esterline-Angus (or similar type) multiple-pen recorder for recording wind direction and miles of movement, precipitation, minutes of sunshine, etc., and in some cases, a 9-pen analog event recorder for wind speed and direction.
(9) Barograph.
(10) Solar radiation spectrometers.
(11) Microprocessors for recording many of the above parameters.
4.3 FFOS's. A minimum thermometer and either a thermograph or hygrothermograph are mounted in a Cotton Region Shelter or a Fruit Frost Shelter (FFS). Some FFOS's have psychrometers. The shelter base should be 4 feet above ground, with the instruments 5 feet above. The thermograph or hygrothermograph chart is changed weekly, at which time the minimum thermometer is read for comparison purposes and reset. FFS's generally have a screen (instead of louvers) on the north-facing side to allow instrument reading without opening the door. FFS's may have a screen or hardware cloth floor, instead of wood.
5.1 WS Form B-43. Personnel at Agricultural Weather Service Centers (AWSC) and Contract Agricultural Weather Offices (CAWO) are responsible for filling out WS Form B-43 with help from the CPM. Meteorologists in Charge at Weather Service Offices and Weather Service Forecast Offices are responsible for completing these in states not served by AWSC's or CAWO's. The completed form will be forwarded through designated channels to the Data Acquisition Division at the regional headquarters. Authorization for the action will be returned through channels to the CPM and the originating office.
When new agricultural forecast areas are formed, the above procedure may be altered as directed by regional headquarters in order to expedite agricultural station reports for the new area.
5.2 AWOS's. WS Form E-15 is used for the observers' daily record at AWOS's and for submission to the National Climatic Data Center (see WSOM Chapter E-41). Soil temperature reporting stations use WS Form F-1OA (see WSOM Chapter B-17) and evaporation stations WS Form E-22 (see WSOM Chapter E-41). The usage of these forms is described in NWS Observing Handbook No. 2.
5.3 MMOS's. Observations from MMOS's are logged by microprocessor6. No forms are filled out. The responsible office will ensure that a permanent record of the observations is maintained.
6. Recording and Transmission of Observations. Observing and reporting procedures for parameters recorded by cooperative observing stations are described in NWS Observing Handbook No. 2. Data may be logged by microprocessors. Methods of transmitting observations are arranged by the primary office using them. Many stations report daily by Touch-Tone or voice telephone.
Collectives of observations are disseminated via the NOAA Weather Wire Service and user dialup to NWS offices, as well as on AFOS circuits using product categories AGO and LCO.
7. Supplies, Maintenance, and Calibration of Equipment. Maintenance and calibration of agricultural station instruments, which are a part of the Cooperative Program Network, are the joint responsibility of the CPM and the appropriate field office. Instrumentation for which the CPM is not responsible will have local maintenance and calibration procedures established by the appropriate NWS field office or by a non-NWS office, such as the agricultural research station or university having responsibility for the station. The maintenance interval, as a general rule, will not exceed 6 months and will vary according to the specific instrumentation. Providing supplies and replacement equipment will also be determined by the appropriate NWS field office if the instrumentation is not part of t-he Cooperative Program Network.
WSOM Issuance
84-9 7-5-84
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