Long Range Forecasting
The success of seasonal forecasts depends on a detailed knowledge of how the atmosphere and ocean interact. As our understanding of the relevant processes has evolved, increasingly complex models have been produced to exploit improved measurements of conditions and provide improved seasonal forecasts. Predicting the behaviour of the ENSO over the months and years ahead offers the best prospect of seasonal forecasting for many parts of the world. In other parts, such as Europe and West Africa, regional sea surface temperatures seem to be the important factor.
The prospect of forecasts on seasonal and longer timescales, for example about whether rainfall or temperature will be above or below average, and by how much, shows enormous potential benefits. These forecasts are generally the products most eagerly sought for longer-term decisions and early warning of potential hazards, but as far any forecast credibility depends on their track record. To be accepted, climate predictions will have to demonstrate skill beyond the climatological experience that is currently used to make decisions.
Empirical methods
The simplest way to forecast departures from the normal climate months to years ahead is to establish statistical rules linking future patterns to current climatic anomalies. Large-scale, slowly varying climatic anomalies, such as in sea surface temperature that can persist for many months, may force changes in atmospheric circulation patterns and hence departures from normal of local climate cycles. At first, this approach was not a great success, but now the growing understanding of what drives ENSO and other forcing patterns has brought improvements. Empirical methods using, for instance, sea surface temperatures assume that local climate will be affected in roughly the same way each time there is a similar large-scale forcing. Their advantage is that they are relatively easy to apply, as they rely entirely on climate statistics and use modest computer resources. There are, however, limitations because the statistical models generally attempt to use a linear approach to predict complex interactions without any specific links to the underlying physical and dynamical processes. This means that they work best when large-scale developments are well and truly under way, but they have difficulty anticipating shifts from, say, warming to cooling or vice versa. As a consequence, they miss sudden developments.
Computer models
A more physically-based approach to seasonal forecasts uses computerized general circulation models (GCMs). In one form of this approach the first step is to predict the development of sea surface temperatures in the tropical Pacific. The predictions may be based on a regional model that considers developments in the tropical ocean in isolation. Once this model has made forecasts of how the Pacific may behave up to a year ahead, the forecast sea surface temperature patterns are used to drive an atmospheric general circulation model to predict how the weather around the globe will respond. These predictions of seasonal weather have produced promising results, especially in the tropics. The improvement of these forecasts has been built on both advances in the models and better observations from the equatorial Pacific Ocean. Significant developments are now being made to develop fully coupled systems in which the ocean, atmosphere and land surface components of the model continually interact with each other to produce a forecast up to several months ahead.
Making the forecasts relevant A challenge to forecasters is to ensure that the forecasts are both timely and understandable to the potential users. Since the most successful forecast methods to date have been mostly associated with ENSO events, it is the lesser developed tropical countries that stand to gain most from these developments. It is important, then, that the predictions must be presented in forms that farmers or fishermen can use; useful predictions cannot rely on computer graphics or statistical arguments, but on statements that can be broadcast over the radio or published in newspapers. In addition, they must be available in time for people to make decisions about what to sow, and in a form that is relevant to making such an important decision. This involves understanding local agricultural practice and variations in climate, and integrating both into a methodology for better decision-making.
Consensus-driven predictions and outlooks
Regional Climate Outlook Forums (RCOFs)
In the late 1990s, an innovative process known as the Regional Climate Outlook Forum (RCOF) was initiated by WMO, National Meteorological and Hydrological Services (NMHSs), regional institutions, and other international organizations. It is a forum that brings together the experts from a climatologically homogeneous region and provides consensus-based, climate prediction and information usually for the season having critical socio-economic significance. This information has been applied to reducing climate-related risks and supporting sustainable development. Such forums have spread to many regions across the world.
Concept
These forums bring together national, regional and international climate experts, on an operational basis, to produce regional climate outlooks based on input from NMHSs, regional institutions, Regional Climate Centres (RCCs) and global producers of climate predictions. By bringing together countries having common climatological characteristics, the forums ensure consistency in the access to and interpretation of climate information. Through interaction with sectoral users, extension agencies and policy makers, RCOFs assess the likely implications of the outlooks on the most pertinent socio-economic sectors in the given region and explore ways how these outlooks could be used.
The core concept of all the RCOFs remains the same: delivering consensus-based user-relevant climate outlook products in real time through regional cooperation and partnership. However, since national and regional capacities are varied and, in some cases, are inadequate to face the task individually, the implementation mechanisms of the RCOFs in different regions have been tailored to meet the local conditions.
The RCOF process, pioneered in Africa, typically includes the following components:
Meetings of the regional and international climate experts to develop a consensus for the regional climate outlook, typically in a probabilistic form;
The Forum proper, that involves both climate scientists and representatives from the user sectors, for identification of impacts and implications, and the formulation of response strategies;
A training workshop on seasonal climate prediction to strengthen the capacity of the national and regional climate scientists;
Special outreach sessions involving media experts, to develop effective communications strategies.
RCOFs also review impediments to the use of climate information, experiences and successful lessons regarding applications of the past RCOF products, and enhance sector-specific applications. These RCOFs then lead to national forums to develop detailed national-scale climate outlooks and risk information including warnings for communication to decision-makers and the public.
RCOFs have facilitated regional cooperation and networking, and have effectively demonstrated the immense mutual benefits of sharing of climate information and experience. Close interaction between the providers and users of climate information and predictions has enhanced feedback from the users to climate scientists, and has catalyzed the development of many user-specific products.
RCOF Users
In many regions, the users benefiting from the RCOFs are true stakeholders, contributing to the organization and growth of the sessions, thus ensuring their sustainability, and applicability to meeting user needs. Typically, RCOFs attract the participation of practitioners and decision-makers from sectors including:
Agriculture and food security
Water resources
Energy production and distribution
Public health
Disaster risk reduction and response
Outreach and communication
Other sectors such as tourism, transportation, urban planning, etc. are increasingly involved.
Based on the needs of specific sectors, specialized, sector-oriented outlook forums, such as the Malaria Outlook Forums (MALOFs) are being held in conjunction with RCOFs in Africa.
RCOFs are in operation in many parts of the world, mainly serving developing countries. These are:
GHACOF: Greater Horn of Africa COF
SARCOF: Southern Africa COF
PRESAO: Prévision Saisonnière en Afrique de lOuest
PRESAC: Prévision Saisonnière en Afrique Centrale
FOCRAII: Forum on Regional Climate Monitoring, Assessment and Prediction for Regional Association II (Asia)
SSACOF: Southeast of South America COF
WCSACOF: Western Coast of South America COF
CCOF: Caribbean COF
FCCA: Foro Regional del Clima de América Central
PICOF: Pacific Islands COF
SEECOF: SouthEastern Europe COF
Regional Climate Change and RCOFs
RCOFs were originally conceived to focus on seasonal prediction, and have significantly contributed to adaptation to climate variability. The concept has the potential to be extended to develop our capacity to adapt to climate change. RCOFs can be effectively expanded to cater to the needs of developing and disseminating regional climate change information products. This concept is already being tested by some RCOFs (e.g., GHACOF). Regional assessments of observed and projected climate change, including the development of downscaled climate change scenario products for impact assessments, can be included in the product portfolio of RCOFs. This potential has already been recognized by the United Nations Framework Convention on Climate Change (UNFCCC) Subsidiary Body on Science and Technology Advice (SBSTA), and constitutes a key element of WMOs contribution to the Nairobi Work Programme on impacts, vulnerability and adaptation to climate change.
El Niño and La Niña
Research conducted over recent decades has shed considerable light on the important role played by interactions between the atmosphere and ocean in the tropical belt of the Pacific Ocean in altering global weather and climate patterns. During El Niño events, for example, sea temperatures at the surface in the central and eastern tropical Pacific Ocean become substantially higher than normal. In contrast, during La Niña events, the sea surface temperatures in these regions become lower than normal. These temperature changes are strongly linked to major climate fluctuations around the globe and, once initiated, such events can last for 12 months or more. The strong El Niño event of 1997-1998 was followed by a prolonged La Niña phase that extended from mid-1998 to early 2001. El Niño/La Niña events change the likelihood of particular climate patterns around the globe, but the outcomes of each event are never exactly the same. Furthermore, while there is generally a relationship between the global impacts of an El Niño/La Niña event and its intensity, there is always potential for an event to generate serious impacts in some regions irrespective of its intensity.
Forecasting and Monitoring the El Niño/La Niña Phenomenon
The forecasting of Pacific Ocean developments is undertaken in a number of ways. Complex dynamical models project the evolution of the tropical Pacific Ocean from its currently observed state. Statistical forecast models can also capture some of the precursors of such developments. Expert analysis of the current situation adds further value, especially in interpreting the implications of the evolving situation below the ocean surface. All forecast methods try to incorporate the effects of ocean-atmosphere interactions within the climate system.
The meteorological and oceanographic data that allow El Niño and La Niña episodes to be monitored and forecast are drawn from national and international observing systems. The exchange and processing of the data are carried out under programmes coordinated by the World Meteorological Organization.
WMO El Niño/La Niña Update
The WMO El Niño/La Niña Update is prepared on a quasi-regular basis (approximately once in three months) through a collaborative effort between WMO and the International Research Institute for Climate and Society (IRI) as a contribution to the United Nations Inter-Agency Task Force on Natural Disaster Reduction. It is based on contributions from the leading centres around the world dealing with this phenomenon. An archive of these updates are available.
The success of seasonal forecasts depends on a detailed knowledge of how the atmosphere and ocean interact. As our understanding of the relevant processes has evolved, increasingly complex models have been produced to exploit improved measurements of conditions and provide improved seasonal forecasts. Predicting the behaviour of the ENSO over the months and years ahead offers the best prospect of seasonal forecasting for many parts of the world. In other parts, such as Europe and West Africa, regional sea surface temperatures seem to be the important factor.
The prospect of forecasts on seasonal and longer timescales, for example about whether rainfall or temperature will be above or below average, and by how much, shows enormous potential benefits. These forecasts are generally the products most eagerly sought for longer-term decisions and early warning of potential hazards, but as far any forecast credibility depends on their track record. To be accepted, climate predictions will have to demonstrate skill beyond the climatological experience that is currently used to make decisions.
Empirical methods
The simplest way to forecast departures from the normal climate months to years ahead is to establish statistical rules linking future patterns to current climatic anomalies. Large-scale, slowly varying climatic anomalies, such as in sea surface temperature that can persist for many months, may force changes in atmospheric circulation patterns and hence departures from normal of local climate cycles. At first, this approach was not a great success, but now the growing understanding of what drives ENSO and other forcing patterns has brought improvements. Empirical methods using, for instance, sea surface temperatures assume that local climate will be affected in roughly the same way each time there is a similar large-scale forcing. Their advantage is that they are relatively easy to apply, as they rely entirely on climate statistics and use modest computer resources. There are, however, limitations because the statistical models generally attempt to use a linear approach to predict complex interactions without any specific links to the underlying physical and dynamical processes. This means that they work best when large-scale developments are well and truly under way, but they have difficulty anticipating shifts from, say, warming to cooling or vice versa. As a consequence, they miss sudden developments.
Computer models
A more physically-based approach to seasonal forecasts uses computerized general circulation models (GCMs). In one form of this approach the first step is to predict the development of sea surface temperatures in the tropical Pacific. The predictions may be based on a regional model that considers developments in the tropical ocean in isolation. Once this model has made forecasts of how the Pacific may behave up to a year ahead, the forecast sea surface temperature patterns are used to drive an atmospheric general circulation model to predict how the weather around the globe will respond. These predictions of seasonal weather have produced promising results, especially in the tropics. The improvement of these forecasts has been built on both advances in the models and better observations from the equatorial Pacific Ocean. Significant developments are now being made to develop fully coupled systems in which the ocean, atmosphere and land surface components of the model continually interact with each other to produce a forecast up to several months ahead.
Making the forecasts relevant A challenge to forecasters is to ensure that the forecasts are both timely and understandable to the potential users. Since the most successful forecast methods to date have been mostly associated with ENSO events, it is the lesser developed tropical countries that stand to gain most from these developments. It is important, then, that the predictions must be presented in forms that farmers or fishermen can use; useful predictions cannot rely on computer graphics or statistical arguments, but on statements that can be broadcast over the radio or published in newspapers. In addition, they must be available in time for people to make decisions about what to sow, and in a form that is relevant to making such an important decision. This involves understanding local agricultural practice and variations in climate, and integrating both into a methodology for better decision-making.
Consensus-driven predictions and outlooks
Regional Climate Outlook Forums (RCOFs)
In the late 1990s, an innovative process known as the Regional Climate Outlook Forum (RCOF) was initiated by WMO, National Meteorological and Hydrological Services (NMHSs), regional institutions, and other international organizations. It is a forum that brings together the experts from a climatologically homogeneous region and provides consensus-based, climate prediction and information usually for the season having critical socio-economic significance. This information has been applied to reducing climate-related risks and supporting sustainable development. Such forums have spread to many regions across the world.
Concept
These forums bring together national, regional and international climate experts, on an operational basis, to produce regional climate outlooks based on input from NMHSs, regional institutions, Regional Climate Centres (RCCs) and global producers of climate predictions. By bringing together countries having common climatological characteristics, the forums ensure consistency in the access to and interpretation of climate information. Through interaction with sectoral users, extension agencies and policy makers, RCOFs assess the likely implications of the outlooks on the most pertinent socio-economic sectors in the given region and explore ways how these outlooks could be used.
The core concept of all the RCOFs remains the same: delivering consensus-based user-relevant climate outlook products in real time through regional cooperation and partnership. However, since national and regional capacities are varied and, in some cases, are inadequate to face the task individually, the implementation mechanisms of the RCOFs in different regions have been tailored to meet the local conditions.
The RCOF process, pioneered in Africa, typically includes the following components:
Meetings of the regional and international climate experts to develop a consensus for the regional climate outlook, typically in a probabilistic form;
The Forum proper, that involves both climate scientists and representatives from the user sectors, for identification of impacts and implications, and the formulation of response strategies;
A training workshop on seasonal climate prediction to strengthen the capacity of the national and regional climate scientists;
Special outreach sessions involving media experts, to develop effective communications strategies.
RCOFs also review impediments to the use of climate information, experiences and successful lessons regarding applications of the past RCOF products, and enhance sector-specific applications. These RCOFs then lead to national forums to develop detailed national-scale climate outlooks and risk information including warnings for communication to decision-makers and the public.
RCOFs have facilitated regional cooperation and networking, and have effectively demonstrated the immense mutual benefits of sharing of climate information and experience. Close interaction between the providers and users of climate information and predictions has enhanced feedback from the users to climate scientists, and has catalyzed the development of many user-specific products.
RCOF Users
In many regions, the users benefiting from the RCOFs are true stakeholders, contributing to the organization and growth of the sessions, thus ensuring their sustainability, and applicability to meeting user needs. Typically, RCOFs attract the participation of practitioners and decision-makers from sectors including:
Agriculture and food security
Water resources
Energy production and distribution
Public health
Disaster risk reduction and response
Outreach and communication
Other sectors such as tourism, transportation, urban planning, etc. are increasingly involved.
Based on the needs of specific sectors, specialized, sector-oriented outlook forums, such as the Malaria Outlook Forums (MALOFs) are being held in conjunction with RCOFs in Africa.
RCOFs are in operation in many parts of the world, mainly serving developing countries. These are:
GHACOF: Greater Horn of Africa COF
SARCOF: Southern Africa COF
PRESAO: Prévision Saisonnière en Afrique de lOuest
PRESAC: Prévision Saisonnière en Afrique Centrale
FOCRAII: Forum on Regional Climate Monitoring, Assessment and Prediction for Regional Association II (Asia)
SSACOF: Southeast of South America COF
WCSACOF: Western Coast of South America COF
CCOF: Caribbean COF
FCCA: Foro Regional del Clima de América Central
PICOF: Pacific Islands COF
SEECOF: SouthEastern Europe COF
Regional Climate Change and RCOFs
RCOFs were originally conceived to focus on seasonal prediction, and have significantly contributed to adaptation to climate variability. The concept has the potential to be extended to develop our capacity to adapt to climate change. RCOFs can be effectively expanded to cater to the needs of developing and disseminating regional climate change information products. This concept is already being tested by some RCOFs (e.g., GHACOF). Regional assessments of observed and projected climate change, including the development of downscaled climate change scenario products for impact assessments, can be included in the product portfolio of RCOFs. This potential has already been recognized by the United Nations Framework Convention on Climate Change (UNFCCC) Subsidiary Body on Science and Technology Advice (SBSTA), and constitutes a key element of WMOs contribution to the Nairobi Work Programme on impacts, vulnerability and adaptation to climate change.
El Niño and La Niña
Research conducted over recent decades has shed considerable light on the important role played by interactions between the atmosphere and ocean in the tropical belt of the Pacific Ocean in altering global weather and climate patterns. During El Niño events, for example, sea temperatures at the surface in the central and eastern tropical Pacific Ocean become substantially higher than normal. In contrast, during La Niña events, the sea surface temperatures in these regions become lower than normal. These temperature changes are strongly linked to major climate fluctuations around the globe and, once initiated, such events can last for 12 months or more. The strong El Niño event of 1997-1998 was followed by a prolonged La Niña phase that extended from mid-1998 to early 2001. El Niño/La Niña events change the likelihood of particular climate patterns around the globe, but the outcomes of each event are never exactly the same. Furthermore, while there is generally a relationship between the global impacts of an El Niño/La Niña event and its intensity, there is always potential for an event to generate serious impacts in some regions irrespective of its intensity.
Forecasting and Monitoring the El Niño/La Niña Phenomenon
The forecasting of Pacific Ocean developments is undertaken in a number of ways. Complex dynamical models project the evolution of the tropical Pacific Ocean from its currently observed state. Statistical forecast models can also capture some of the precursors of such developments. Expert analysis of the current situation adds further value, especially in interpreting the implications of the evolving situation below the ocean surface. All forecast methods try to incorporate the effects of ocean-atmosphere interactions within the climate system.
The meteorological and oceanographic data that allow El Niño and La Niña episodes to be monitored and forecast are drawn from national and international observing systems. The exchange and processing of the data are carried out under programmes coordinated by the World Meteorological Organization.
WMO El Niño/La Niña Update
The WMO El Niño/La Niña Update is prepared on a quasi-regular basis (approximately once in three months) through a collaborative effort between WMO and the International Research Institute for Climate and Society (IRI) as a contribution to the United Nations Inter-Agency Task Force on Natural Disaster Reduction. It is based on contributions from the leading centres around the world dealing with this phenomenon. An archive of these updates are available.
