Global Observing System (GOS)

Scope  

The Global Observing System (GOS) provides observations on the state of the atmosphere and ocean surface from the land-based and space-based instruments. This data is used for the preparation of weather analyses, forecasts, advisories and warnings, and for the climate monitoring and environmental activities carried out through other programmes as well as by other international organizations. Global Observing System is operated by National Meteorological and Hydrological Services (NMHSs), national or international satellite agencies, and involves several consortia dealing with specific observing systems or specific geographic regions. 

Objectives

The objectives of WIGOS, thus GOS as well, are:

• to improve and optimize global systems for observing the state of the atmosphere and the ocean surface to meet the requirements for the preparation of increasingly accurate weather analyses, forecasts and warnings, and for climate and environmental monitoring activities carried out under other programmes as well as by other international organizations; and
• to provide for the necessary standardization of observing techniques and practices, including the planning of networks on a regional basis to meet user requirements with respect to quality, spatial and temporal resolution and long-term stability.  

Background

Since the establishment of the World Weather Watch (WWW) in 1963, the Global Observing System (GOS) has been the major mechanism for providing continuous and reliable observational data worldwide. The Global Observing System started with a relatively narrow set of observational requirements in support of mainly synoptic, mesoscale and short-term weather forecasts. Over the past four decades, however, the World Weather Watch, and more specifically its Global Observing System, have immensly developed technological capabilities in response to requirements that have evolved within WMO and beyond.

Although the Global Observing System continues to be the foundation on which all meteorologists depend, there has been gradual yet steady erosion of the surface-based observing networks during the past few years in some parts of the world. At the same time, the emergence of new technologies and techniques has facilitated observations and measurements with greater resolution and accuracy. This, together with greatly increased computing power, has greatly benefited Numerical Weather Prediction (NWP) by making possible the development of highly sophisticated assimilation techniques that can accept and evaluate observations from any source made at any time. The Global Basic Observing Network (GBON) was established in 2023 to address some of the deficiencies of the GOS. 

The Global Climate Observing System (GCOS) requirements for increased long-term reliability and accuracy are being fulfilled by the Global Observing System.

Components

Surface observations  

Through the surface-based sub-system, there are approximately 17 500 stations/platforms making observations at or near the Earth’s surface, often hourly, of meteorological parameters such as atmospheric pressure, wind speed and direction, air temperature and relative humidity. Data from these stations are exchanged globally in real-time through WIS. 

Upper-air observations  

From a global network of about 1 000 upper-air stations, radiosondes, attached to free-rising balloons, make measurements of pressure, wind velocity, temperature and humidity from just above ground to heights of 30 km, or above. Over two thirds of the stations make observations at 00 UTC and 12 UTC.  In ocean areas, radiosonde observations are taken by about 15 ships, which mainly ply the North Atlantic, fitted with automated shipboard upper-air sounding facilities (ASAP). A subset of upper-air stations comprises the GCOS Upper-air Network (GUAN).  

Marine observations

Over the oceans, the GOS relies – in addition to satellites – on ships, moored and drifting buoys, and stationary platforms. Observations made by around 4 000 ships recruited under the WMO Voluntary Observing Ship Programme, collect many of the same variables as those at surface land stations with the important additions of sea surface temperature, wave height, and wave period. The operational drifting buoy programme comprises about 1 200 drifting buoys provides about 27 000 sea surface temperature and 14 000 sea level pressure reports per day.

In addition, Tsunami Warning Systems, owned and operated by Members, have been established under the aegis of the IOC of UNESCO, in cooperation with the WMO in the Pacific and Indian oceans, and are planned in other maritime areas; they include a network of real-time surface and deep-sea level sensors for the detection, early warning and monitoring of tsunamis.  

Aircraft-based observations

In collaboration with International Civil Aviation Organization (ICAO), the International Air Transport Association (IATA) and commercial and other airlines, aircraft-based observations are received from over 4 000 aircraft, providing reports of pressure, winds, temperature, humidity, turbulence and other parameters during flight. The Aircraft Meteorological Data Relay (AMDAR) system makes high-quality observations of air temperature and wind speed and direction at cruising level, as well as at selected levels in ascent and descent. The amount of data from aircraft has increased to an estimated 700 000 reports per day corresponding to approximately 90 000 profiles of AMDAR data at 550 airports globally. Providing great potential for measurements in places where there are a little or no radiosonde data, these systems are making a major contribution to the upper-air component of GOS.

For more information: AMDAR Observing System

Satellite observations

Space-based meteorological observations are performed within satellite programmes implemented by space agencies. International coordination among satellite operators is achieved within the Coordination Group for Meteorological Satellites (CGMS), the primary goal of which is to support operational weather monitoring and forecasting as well as climate monitoring, in response to requirements formulated by WMO.

The space-based backbone component of WIGOS includes constellations of Sun-synchronous low Earth orbit (LEO) satellites in three orbital planes and a ring of geostationary Earth orbit (GEO) satellites providing complete coverage outside the polar areas, complemented by satellites in other orbital planes and satellites in drifting orbits completing requirements for operational meteorology. 
GEO VIS/IR imaging is particularly suited for very frequent and constant sampling (at sub‑hourly or minute rates) as necessary for rapidly evolving phenomena like detecting movement and evolution of clouds, severe weather, volcanic eruptions and forest fires. The requirement for the complete global (excluding polar regions) imaging from the geostationary orbit needs six regularly‑spaced spacecraft. In an operational constellation, backup satellites are required to provide redundancy above this minimum.
The Sun‑synchronous orbit provides global coverage necessary for applications such as global numerical weather prediction (NWP), polar meteorology, and climatology. For these applications, very frequent sampling is less critical than global coverage and high accuracy. Additional advantages of Sun‑synchronous and other low Earth orbits are the capability to perform active sensing in the MW (radar) and optical (lidar) ranges and limb measurements of the higher atmosphere.

Improvements in NWP in particular have made it possible to develop increasingly sophisticated methods of deriving temperature and humidity information directly from the satellite radiances. In the recent years, impressive progress was made in weather and climate analysis and forecasts including warnings for hazardous weather phenomena (heavy rain, storms, cyclones) affecting all populations and economies. This is largely attributable to space-borne observations and their assimilation into NWP models.
In order to provide operational continuity in the space-based meteorological observations the currently operational satellites are constantly being replaced by new satellites of the existing generations or by new-generation satellite systems, providing users with new types of data with increased observation capabilities resulting in overall data volumes that are one or more orders of magnitude higher than those of the previous generation.

For a list of currently operational and planned meteorological and related environmental satellites and their parameters, please refer to the WMO OSCAR/Space database.

For more information: WMO Space Programme.

Weather Radar Observations

Weather radars have been proved to be invaluable in providing data of high-resolution in both space and time over relatively large areas, especially in the lower layers of the atmosphere. These instruments are for example used in real-time estimation and short-term forecasting of rainfall amounts. They are also uniquely capable of observing the development of several severe weather phenomena, such as severe convective weather or tropical storms. Precipitation-related data products from radars can enable or enhance the detection and prediction of flash floods. These characteristics make weather radars essential systems to support issuance of timely high-impact weather warnings.

In addition to their primary functions, operational weather radars can measure winds within precipitation, complementing other upper-air measurement technologies, such as radiosondes and wind profiler radars. Furthermore, the implementation of dual-polarization technology in weather radar systems has brought several benefits, including, but not limited to the improved detection of precipitation types, more accurate rainfall estimation, and improved overall quality of radar data. Weather radars have become a crucial component of modern national and regional observing networks.  

Other observation platforms

GOS also includes solar radiation observations, lightning detection and tide-gauge measurements. Wind profiler radars provide continuous real-time profiles of wind direction and speed from heights near the surface up to the troposphere. These profiles complement other upper-air wind profiling methods, such as radiosondes, and are a valuable input to Numerical Weather Prediction systems. As opposed to weather radars, these instruments can make useful measurements even in the absence of precipitation, by detecting echoes scattered from irregularities of the refractive index of air. This clear air sensing capability is a truly unique feature of this radar. In addition, wind profiler radar can also measure winds by detecting echoes from other targets such as precipitation.  

In addition, wind profilers have proven useful in making observations between balloon-borne soundings and have great potential as a part of integrated networks. 

Vision and Implementation Plan

Vision for the WMO Integrated Global Observing System in 2040 provides high-level targets to guide the evolution of WIGOS in the coming decades. It presents a likely scenario of how user requirements for observational data may evolve in the WMO domain over the next several decades and an ambitious but technically and economically feasible vision for an integrated observing system that will meet them. With this information, NMHSs, space agencies and other observing system developers will be able to adapt their planning efforts accordingly and will be able to make the decisions necessary to implement this integrated system.  

High–Level Guidance on the Evolution of Global Observing Systems during the period 2023–2027 in response to the Vision for the WMO Integrated Global Observing System (WIGOS) in 2040. It provides guidance to WMO Members for key activities to be implemented within the next five years to accomplish the Vision for WIGOS in 2040.2 The guidance consists of principles of a general nature that should be considered for the development of implementation plans by Members, agencies, and other operators of observing networks. It also identifies urgent specific actions arising as a consequence of WMO’s Earth System approach and priorities of WIGOS, WMO programmes; and existing data gaps.  

OSCAR/Surface  

OSCAR/Surface is the official repository of metadata on surface-based meteorological and climatological observations that are required for international exchange. Observational metadata, i.e., information on the capabilities of observing stations / platforms and their instruments and methods of observation, are routinely submitted to and maintained in OSCAR/Surface by WMO Members. OSCAR/Surface replaces the WMO Publication No. 9, Volume A, Observing Stations and WMO Catalogue of Radiosondes, which is now obsolete, and highlights the much wider scope of all the observing systems contributing to WIGOS. 

For more information: OSCAR/Surface