APPENDIX E

PILOT BALLOON AND RAWINSONDE OBSERVATION
ENCODING AND DECODING

TABLE OF CONENTS

Index

E.1   Introduction
E.2   WMO Code Forms
E.3   Symbolic Forms for Data Groups
E.4   References to Level Coding
E.5   Basic Code Construction

E.5.1   Versions of the PILOT Messages
E.5.2   Versions of the TEMP Messages

E.6   Numbering System of International Code Tables

Appendix E-I   Code Form for PILOT Observations

E-I.1     CODE FORM: PILOT Parts A,B,C, and D by Section Number
E-I.2     CODE FORM: PILOT Upper Wind Report Code Forms

E-I.2.1 Section 1 - Identification and Position Data
E-I.2.2 Section 2 - Data for Standard Isobaric Surfaces
E-I.2.3 Section 3 - Data for Max Wind Levels E-13
E-I.2.4 Section 4 - Data for Fixed Additional Levels
E-I.2.5 Section 5 - Regional Code Groups
E-I.2.6 Section 6 - National Code Groups

Appendix E-II    Code Form for TEMP Rawinsonde Observations

E-II.1     CODE FORM: TEMP Parts up to and including the 100 hPa Surface
                     and Parts C and D Above the 100 hPa Surface
E-II.2     CODE FORM: TEMP Upper-level Pressure, Temperature, Humidity
                     and Wind Report Code Forms

E-II.2.1 Section 1 - Identification and Position Data
E-II.2.2 Section 2 - Data for Standard Isobaric Surfaces
E-II.2.3 Section 3 - Data for Tropopause Level(s)
E-II.2.4 Section 4 - Data for Max Wind Levels
E-II.2.5 Section 5 - Data for Additional Levels (Temperature)
E-II.2.6 Section 6 - Data for Additional Levels (Winds)
E-II.2.7 Section 7 - Data on Sea Surface Temperature and Sounding System
E-II.2.8 Section 8 - Cloud Data
E-II.2.9 Section 9 - Code Groups Developed Regionally
E-II.2.10 Section 10 - Code Groups Developed Nationally

Appendix E-III   Required Code Tables for PILOT and TEMP Code Forms

Table of Contents, Appendix E-III

APPENDIX E

RAWINSONDE AND PILOT BALLOON OBSERVATION
ENCODING AND DECODING

E.1 Introduction. Coded messages are used for the international exchange of meteorological information comprising observational data provided by the World Weather Watch (WWW) Global Observing System and processed data provided by the WWW Global Data-processing System. Coded messages are also used for the international exchange of observed and processed data.

The WMO, through its Commission for Basic Systems (CBS), prescribes standard formats for the exchange of meteorological information. These formats (codes) are described in the WMO Manuals on Codes Volumes I and II (WMO No. 306) [Ref. 9]. The United States, as a member of the WMO, uses these codes for the exchange of upper-air data.

Rules concerning the selection of code forms to be exchanged for international purposes, and the selection of their symbolic words, figure groups and letters, are contained in Volume I of the Manual on Codes (issued with separate covers as Volume I.1 -- Part A, and Volume I.2 -- Part B and Part C.)

Apart from the international codes, several sets of regional codes exist which are intended for exchanges only within a specific WMO Region. These codes are contained in Volume II of the Manual on Codes. Volume II also contains descriptions of:

-- Regional procedures for the use of international code forms;
-- National coding practices in the use of international or regional codes of which the WMO Secretariat has been informed;
-- National code forms.

E.2 WMO Code Forms. Each WMO code form is identified by the letters FM followed by a complex term composed of an Arabic numeral followed by a Roman numeral and a short descriptor. The Arabic numeral assigns classes to the various code forms. In general the 10-series pertains to codes related to surface observations. The 20-series pertains to radar observations. The 30-series pertains to upper-air observations involving the tracking of a balloon or sounding device. However, this convention does not continue through the rest of the code-series so should not be relied upon as a hard and fast rule. The sub-classes in each series pertain to specific types of observations within those classes such as 32-PILOT (an upper wind observation); 35-TEMP (a rawinsonde observation from a fixed land station); 36-TEMP SHIP (a rawinsonde observation from a ship; 37-TEMP DROP (a dropsonde observation from an aircraft); and 38-TEMP MOBIL (a rawinsonde observation from a mobile land station). The Roman numeral indicates at which session of the WMO Commission the code was either adopted or last revised. The principal function of the Roman numeral is to enable users to determine if they have the most recently published version of the code.

E.3 Symbolic Forms for Data Groups. The codes are composed of a set of CODE FORMS and BINARY CODES made up of SYMBOLIC LETTERS (or groups of letters) representing meteorological or, as the case may be, other geophysical elements. In messages, these symbolic letters (or groups of letters) are transcribed into figures indicating the value or the state of the elements described. SPECIFICATIONS have been defined for the various symbolic letters to permit their transcription into figures. In some cases, the specification of the symbolic letter is sufficient to permit a direct transcription into figures. In other cases, it requires the use of CODE FIGURES, the specifications of which are given in CODE TABLES. Furthermore, a certain number of SYMBOLIC WORDS and SYMBOLIC FIGURE GROUPS have been developed for use as code names, code words, symbolic prefixes or indicator groups. The number of letters used in the symbolic form (exclusive of subscripts or superscripts) always equals the number of digits that will appear in the numeric form of an actual coded message.

Parts and sections of code forms may have been built up from a number of well-defined components, each comprising a different type of coded information. Components which can be transmitted as termed a separate report are 'parts' and carry special identification groups. Code forms, or their parts, can be divided into sections which may be omitted from the report under certain conditions and therefore carry a symbolic indicator figure or group.

Code form groups in round brackets are drop-out items and may or may not be included, depending on specified conditions. The absence of round brackets means that the group concerned is always included, as determined by international decision; these decisions are indicated in the regulations appearing under each code form.

Unless indicated otherwise, specifications apply to all forms of the Pilot Balloon and Rawinsonde codes. Code Tables, if needed, are referenced at the end of the specification.

E.4 References To Level Coding. The following code forms and tables contain both explicit and implicit references to the three types of levels: standard, mandatory significant, and additional. Standard levels are covered explicitly in paragraphs E-I.2.2 and E-II.2.2. Additional levels are covered explicitly in paragraphs E-I.2.4 and E-II.2.5 and .6. Some of the mandatory significant levels. such as the surface and tropopause, are dealt with explicitly, while the remainder are referred to implicitly in the paragraphs on Additional Levels.

E.5 Basic Code Construction for Formatted Messages

E.5.1 Versions of the PILOT Messages. Messages from fixed land stations which contain only wind data are called PILOT messages. Those transmitted from ships are labelled PILOT SHIP. Those from mobile land stations are PILOT MOBIL. The three versions of the PILOT code are:

• FM 32-IX PILOT, an upper wind report from a land station;
• FM 33-IX PILOT SHIP, an upper wind report from a ship;
• FM 34-IX PILOT MOBIL, an upper wind report from a mobile land station.

A report from a fixed land station which has been assigned a WMO location index number shall report in FM 32 PILOT. Temporary land stations, tasked and equipped to take and transmit upper level wind observations, shall use FM 34 PILOT MOBIL. There is no provision in any of the upper-level wind codes for reports from an instrument released from an aircraft.

E.5.1.1 PILOT Observations. The relationship of the four parts of the code form and component sections that can be a part of a given part follow:

The code form consists of the following four parts:

(Each part can be transmitted separately.)

The code form is divided into the following sections and indicated Parts:

E.5.1.2 The full Code Form for PILOT Observations is contained in APPENDIX E-I. Where possible, sections and parts are combined in the APPENDIX E-1 to minimize largely redundant symbolic letters, definitions, and regulations.

E.5.2 Versions of the TEMP Messages. Each code form is further specified by a character string that describes the code form more succinctly. For example, the rawinsonde coded messages are described as TEMP messages. The three versions of the TEMP code described in this Handbook are:

• FM 35-X Ext. TEMP, an upper level pressure, temperature, humidity and wind report from a land station;
• FM 36-X Ext. TEMP SHIP, an upper level pressure, temperature, humidity and wind report from a sea station;
• FM 38-X Ext. TEMP MOBIL, an upper level pressure, temperature, humidity, and wind report from a mobile land station.

Temporary land stations are established to support special studies or other short-term activities. Short-term activities are usually less than six months in duration.

E.5.2.1 The relationship of the four parts of the code form and component sections that can be a part of a given TEMP message are outlined in the succeeding paragraphs.

The code form consists of the four parts as follows:

The code form is further divided into the following sections and their associated parts:

E.5.2.2 The full Code Form for TEMP Observations is contained in Appendix E-II. Where possible, sections and parts are combined to minimize largely redundant symbolic letters, definitions, and regulations.

E.6 Numbering System of International Code Tables. When coding a report, symbolic letters or groups are replaced by figures, which specify the value or the state of the corresponding element. In some cases the specification of the symbolic letter (or group of letters) is sufficient to permit a direct transcription into figures, e.g. GG or PPP. In other cases, these figures are obtained by means of special Code Table for each element.

The Code Tables are also used for decoding incoming reports thus making available the information contained therein.

The Code Tables are numbered, each bearing a number consisting of four figures from 0100 up to 5299 and allotted in the alphabetical order of the symbols to which the Code Tables correspond. The attribution of the numbers is done in accordance with the following system:

(1) The first two figures represent the number of the main letter of the symbol in alphabetical order. Capital letters are given an odd number, and small letters an even number: 01 for A, 02 for a, 03 for B, 04 for b.....51 for Z and 52 for z.

(2) The last two figures are allocated in accordance with the following scheme:

00 to 01 are reserved for Code Tables corresponding to a symbol composed of one letter only (X or x, for instance);

02 to 30 are reserved for Code Tables corresponding to symbols of the forms X_A to X_Z, x_A to x_Z and derived symbols such as X_AO or x_AO;

31 to 60 are reserved for Code Tables corresponding to symbols of the forms X_a to X_z, x_a to x_z and derived symbols such as X_aO or x_AO

61 to 70 are reserved for Code Tables corresponding to symbols of the forms X₀ to X_n, or x₀ to x_n, n being any number;

71 to 99 are reserved for Code Tables corresponding to symbols of the forms X', XX, XXX, x', xx, xxx or any similar forms such as X_bX_b, X₀X₀X₀, x_bx_b, x₀x_ox_o.

The numbers attributed to the Code Tables for the different elements specific to upper-air observations for PILOT and TEMP observations are provided in Appendix E-III.

Besides the specifications given by the Code Tables in worldwide use, other sets are established for regional use, which are numbered with a three-figure number ranging from 120 to 800, and are given in Ref. 9: Volume II.

Appendix D
Appendix E-I
Appendix F
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