TO :        All Holders of Operations Manual

SUBJECT: Transmittal Memorandum for Operations Manual Issuance 82-2

1. Material Transmitted:

Chapter B-10, Surface Observing Program (Land).

2. Summary:

This chapter provides an updated description of the surface data acquisition programs managed by the National Weather Service.

3. Effect on Other Instructions:

Cancels WSOM Chapter 8-10, TM 74-3, dated January 21, 1974, and OML 5-79, dated March 27, 1979,
filed with B-10.
 
 
 
 
 
 

Richard E. Hallgren
Director, National Weather Service
 

Issue Date Org. Code             NATIONAL WEATHER SERVICE    Part     Chap.
1-7-82         W52x1                     Operations Manual                            B         10

Table of Contents:

1. General

1.1 Purpose
1.2 Organization of Chapter

2. Surface Observation Networks

2.1 National Meteorological Center (NMC) Network
2.2 National Severe Storms Forecast Center (NSSFC) Network
2.3 Regional Network
2.4 Substation Network

3. Types of Observing Stations

3.1 National Weather Service Observing Stations
3.2 Federal Aviation Administration (FAA) Observing Stations
3.3 Supplementary Aviation Weather Reporting Stations (SAWRS)
3.4 Contract Stations
3.5 Automatic Meteorological Observing Stations
3.6 Agricultural Weather Stations
3.7 Fire Weather Stations
3.8 Marine Reporting Stations (MARS)
3.9 Combinations of Various Types of Stations

4. Types of Observations

4.1 Synoptic Observations
4.2 Basic Weather Observations
4.3 Aviation Observations
        4.3.1 Limited Aviation Observations
        4.3.2 Supplementary Aviation Observations
4.4 Climatological and Hydrologic Observations
4.5 Local Service and Special Purpose Observations

5. Elements Observed

5.1 Sky Condition
5.2 Visibility
5.3 Weather and Obstructions to Vision
        5.3.1 Precipitation Measurements
5.4 Pressure
5.5 Temperature and Dew Point
5.6 Wind
5.7 Evaporation
5.8 Sunshine
5.9 Solar Radiation
5.10 Soil Temperature

Exhibit:

B-10-1 Content of Observations

1. General.

1.1 Purpose. This chapter describes the surface data acquisition program managed by the National Weather Service (NWS) at land stations. Excluded, however, are short-term data acquisition programs and those operated primarily for research, e.g., ozone observations.

1.2 Organization of Chapter.

Section 2 - Describes the major data acquisition networks.

Section 3 - Describes the type of stations which make up the networks.

Section 4 - Identifies the various types of observations made by stations in the networks.

Section 5 - Summarizes the individual elements observed.

Exhibit B-10-1 indicates the elements in the different types of observations and the source of instructions.

2. Surface Observation Networks.

2.1 National Meteorological Center (NMC) Network. This network provides observations required by NMC for the preparation of synoptic-scale surface analysis. Within the 48 conterminous states and Alaska, the NMC requirement is for observations spaced approximately 100 miles apart and taken every 3 hours. In Hawaii, the requirement is for observations every 6 hours. The most important observational parameters required of stations in this network are temperature, dew point, wind speed and direction, and pressure.

2.2 National Severe Storms Forecast Center (NSSFC) Network.  This network provides the observations required by the NSSFC to detect and define mesoscale storms and related severe weather.  This requirement is for hourly observations 24 hours a day supplemented by special observations. The required spacing of stations in this network depends on several variables, e.g., frequency of severe storms, population, radar coverage, etc. In addition to the elements required in the NMC network, sky cover, visibility, weather and obstructions to vision, and precipitation amounts are necessary for the NSSFC network.

2.3 Regional Network. This network provides data required by weather service forecast offices (WSFO), and by weather service offices (WSO), for local use, not provided by either the NMC or NSSFC networks. The frequency, spacing, and content of observations in this network are variable.

2.4 Substation Network. This network is made up of three networks: the a-network, the basic climatic network; the b-network, the basic hydrologic network; and the c-network, a local service network. Details on these networks are given in Chapter B-17, Substation Management.

3. Types of Observing Stations.

3.1 National Weather Service Observing Stations. At these stations, observations are made by NWS employees or contract observers at NWS facilities. The observation program or programs at these stations are of primary priority and can be made to satisfy the requirements of any network or special program. The only limiting factors are available staff and acceptable observing sites.

3.2 Federal Aviation Administration (FAA) Observing Stations. These are FAA facilities at which surface observations are made. However, the observations are lower in priority than other FAA duties. The observations made at FAA Flight Service Stations are usually basic observations and may satisfy requirements of the NMC, NSSFC, or regional networks. Observations made at FAA Air Traffic Control Towers are normally limited aviation observations and only rarely satisfy fully the requirements of the NSSFC or regional networks. These observations (from towers) will not satisfy the NMC network requirements because of the lack of certain key elements. Details on the operation of observational programs at FAA stations are given in chapter B-13.

3.3 Supplementary Aviation Weather Reporting Stations (SAWRS). SAWRS make observations so that aircraft operations at certain locations comply with the weather requirements of the Federal Aviation Regulations (FAR's). The observation program at these stations is limited to those observations and elements required for local operation. Because of this, SAWRS observations do not satisfy network requirements for data. Details on the operation of SAWRS are given in chapter B-14.

3.4 Contract Stations. At some locations, the NWS contracts for a full observing program identical to that provided by NWS-staffed stations. Equipment and facilities are provided by the NWS. At other locations, local citizens or organizations make observations required by the NWS on an irregular or part-time basis. Contract stations include two types: (1) weather service contract meteorological observatories (WSCMO) which provide the same observations provided by WSO's and weather service meteorological observatories (WSMO), and (2) supplemental contract stations which increase the areal distribution of observations for operational or climatological use in the NMC, NSSFC, regional, or substation networks. Details on the operation of supplemental contract stations are given in chapters B-15 and B-17.

3.5 Automatic Meteorological Observing Stations. These observing stations employ automatic observing systems to sense certain elements and format them for transmission. Automatic systems in use are: automatic meteorological observing system (AMOS), remote automatic meteorological observing system (RAMOS), and automatic observing station (AUTOB). The stations are generally not staffed with personnel; however, when staffed, the automated observation may be supplemented by manually entered data. Observations from unstaffed stations completely satisfy the requirements of the NMC network and satisfy some of the requirements of the NSSFC network. Except in special cases, they do not satisfy the requirements of the regional network. Observations from staffed stations satisfy the requirements of all networks.

3.6 Agricultural Weather Stations. These stations are established by the NNW to provide specialized support to the agricultural weather program. To provide such data, NWS utilizes a number of cooperative observing stations in representative agricultural areas and within or near various crops or agricultural enterprises. As far as possible, the stations used are already integral parts of the national climatological and hydrological networks; where necessary to obtain additional pertinent data, sites are established for the specific purpose of supporting the agricultural weather program. Details on these stations are given in chapter B-18.

3.7 Fire Weather Stations. Fire Weather Observation Stations provide the specialized weather observations for fire weather forecasts, wildfire control and suppression, and various other wildlands management operations. The data are also used by wildlands management agencies for fire danger ratings. These stations may be either staffed observation stations operated by the fire control agencies or the NWS or unstaffed remote automatic weather stations (RAWS) which are operated by the various Federal and state wildlands management agencies. Details on the operation of these stations are given in chapter B-19.

3.8 Marine Reporting Stations (MARS). These stations support coastal marine weather services. They are established by the NWS to provide data on weather conditions along coastal areas or on inland bodies of water -- data that is not available from stations in other networks. Some of these stations provide special service during coastal storms, support the National Hurricane Center, and are used in the NSSFC network. Details on these stations are given in chapters B-16 and B-90.

3.9 Combinations of Various Types of Stations. Observing programs may be established that combine any of the above types of stations. For example, at the same location, observations may be taken at certain times by a Weather Service Office and at other times by a flight Service Station. However, at no time will two different parties make official observations of the same elements at the same time for the same location.

4. Types of Observations.

4.1 Synoptic Observations. Synoptic observations serve two purposes: they provide the data used in weather analysis/ prediction and the data required to fulfill the NWS commitment for international exchange of data. There are two types of synoptic observations taken at land stations -- primary and intermediate. Primary synoptic observations are taken at 0000, 0600, 1200, and1800 GMT. Intermediate synoptic observations are abbreviated synoptic observations taken at 0300, 0900, 1500, and 2100 GMT. These observations completely satisfy the data requirements of the NMC network and some of the requirements of the NSSFC network and the regional network. The elements are observed in accordance with federal Meteorological Handbook (FMH) No. 1, Surface Observations; and are encoded into the synoptic code in accordance with FMH No. 2, Synoptic Code.

4.2 Basic Weather Observations. Basic weather observations are made in support of the various service functions of the NWS, e.g., public services, weather briefings, weather warnings, etc. These observations also satisfy requirements of the NSSFC and regional networks. These observations are made, recorded, and coded in accordance with FMH No. 1.

4.3 Aviation Observations. Aviation observations are an abbreviated version of the basic weather observations. While the basic weather observations also serve aviation purposes, the aviation observations are made primarily to serve aviation requirements. There are two types of aviation observations: limited and supplementary.

4.3.1 Limited Aviation Observations. These observations are used to support aviation operations in a terminal controlled airspace, and the observation schedule depends on the operating hours of the control tower. Where limited aviation observations are taken 24 hours a day, the observations can also satisfy some of the requirements of the NSSFC network. Limited aviation observations are made in accordance with FMH No. 9, Aviation Weather Observations.

4.3.2 Supplementary Aviation Observations. Supplementary aviation observations include only those elements of the basic weather observation required to satisfy FAR's. Supplementary aviation observations can be expanded when the cooperator (e.g., an air taxi operator or commuter airline) requires a terminal forecast for the station. Like limited aviation observations, supplementary aviation observations may be made hourly. However, most often they are made at irregular intervals -- when needed by the cooperator -- and are usually disseminated locally. Supplementary aviation observations are made in accordance with FMH No. 9, Aviation Weather Observations.

4.4 Climatological and Hydrologic Observations. These observations are made to provide data to meet climatological and hydrologic requirements of the NWS (see chapter B-17). Observations are usually made once a day with more frequent observations made to report significant weather occurrences. Data from climatological observations and some hydrologic sites are collected by mail, but data from hydrologic observations used in river and flood forecasting are generally transmitted by telephone to designated NWS offices for relay to River Forecast Centers. Climatological and hydrologic observations are made in accordance with WSOH No. 2, Substation Observations.

4.5 Local Service and Special Purpose Observations. A variety of observations are made in support of special forecasting, warning, or public service activities of the NWS. Such surface observations are included in chapters B-21 and B-90.

5. Elements Observed.

5.1 Sky Condition. The observation of sky condition varies according to the types of observation program. The observation can consist of any of the following:

        a. Amount of clouds (either in eighths of the sky covered by clouds in the synoptic observation or tenths of the sky covered by clouds in other observations).

        b. Height of clouds (in feet above the ground).

        c. Type of clouds (in accordance with WMO definitions).

        d. Ceiling (in feet above the ground).

        e. Movement of clouds.

        f. AUTOB cloud amount and height measurements -- taken only directly overhead the detector to a vertical height of 6,000 feet. The amount and height are weighted averages of the conditions that occur over the ceilometer in the 30 minutes before the report is generated. See Guide to AMOS, RAMOS and AUTOB Observations, Silver Spring, Md., June 1981.

Sky condition is observed and reported in accordance with FMH No. 1, FMH No. 2, and FMH No. 9.

5.2 Visibility. Visibility is observed and reported in accordance with FMH No. 1, FMH No. 2, and FMH No. 9. AUTOB reports an index of visibility. The difference between an AUTOB visibility measurement and a human visibility observation is explained in the Guide to AMOS, RAMOS, and AUTOB Observations, Silver Spring, Md., June 1981.

5.3 Weather and Obstructions to Vision. The occurrence of weather and obstructions to vision is observed by nearly all stations. The definitions of the phenomena are given in FMH No. 1 and FMH No. 9.

5.3.1 Precipitation Measurements. The observation of the amount of precipitation varies considerably according to the purpose of the observing operations, e.g., at LAWRS and SAWRS, the amount of precipitation is not observed at all. At other stations, the observations may consist of the accumulation, rate of accumulation, time of occurrence, and duration. Other measurements made: snow depth, water-equivalent of snowfall, and water-equivalent of snow on the ground. Details on observing and reporting precipitation measurements are given in FMH No. 1, FMH No. 2, and WSOH No. 2.

5.4 Pressure. Atmospheric pressure is measured and recorded in several different forms. Measurements are made of: station pressure, sea-level pressure, altimeter setting, and pressure change and tendency. Instructions for measuring or determining and reporting pressure are given in FMH No. 1, FMH No. 2, and FMH No. 9.

5.5 Temperature and Dew Point. The ambient air temperature is observed at most stations. The temperature of the dew point is determined at most stations in the NMC, NSSFC, and regional networks. These data are observed in accordance with FMH No. 1, FMH No. 9, and WSOH No. 2.

5.6 Wind. The basic observation of wind includes the direction in tens of degrees with respect to true north and the speed (1-minute average). At some stations, the maximum wind speed occurring during the day is recorded at stations having a continuous wind speed recorder. At stations equipped with an operations recorder, the fastest mile of wind is determined. Peak wind speed is reported at automated stations. Wind is observed and reported in accordance with FMH No. 1, FMH No. 2, FMH No. 9, and WSOH No. 2.

5.7 Evaporation. These measurements are made only at selected stations. The observation consists of measuring the amount of water evaporating from the pan each day. Details on the observation of evaporation are given in WSOH No. 2.

5.8 Sunshine. The observation of sunshine consists of recording the minutes of sunshine occurring each day. Such recordings are made at selected NWS stations. FMH No. 1 gives details on the observing procedure.

5.9 Solar Radiation. A network of selected stations measures the global, direct, and diffuse components of solar radiation. Details are contained in WSOH No. 3, Solar Radiation Observations.

5.10 Soil Temperature. Soil temperature measurements are made at selected stations, usually agricultural weather stations or basic climatic stations. The observation consists of measurements of maximum and minimum or ambient temperatures at selected depths in the soil. Details on observing this element are given in WSOH No. 2.