Short-term Climate Prediction Research Articles

Atmospheric Predictability of Seasonal, Annual, and Decadal Climate Means and the Role of the ENSO Cycle: A Model Study

The characteristics of extratropical low-frequency variability are examined using a comprehensive atmospheric general circulation model. A large experiment consisting of 13 45-yr-long integrations forced by prescribed sea surface temperature (SST) variations is analyzed. The predictability of timescales of seasonal to decadal averages is evaluated. The variability of a climate mean contains not only climate signal arising from external boundary forcing but also climate noise due to the internal dynamics of the climate system, resulting in various levels of predictability that are dependent on the forcing boundary conditions and averaging timescales. The focus of this study deviates from the classic predictability study of Lorenz, which is essentially initial condition sensitive. This study can be considered to be a model counterpart of Madden’s “potential” predictability study. The tropical SST anomalies impact more on the predictability over the Pacific/North America sector than the Atlantic/Eurasia sector. In the former sector, more significant and positive impacts are found during El Niño and La Niña phases of the ENSO cycle than during the ENSO inactive period of time. Furthermore, the predictability is significantly higher during El Niño than La Niña phases of the ENSO cycle. The predictability of seasonal means exhibits large seasonality for both warm and cold phases of the ENSO cycle. During the warm phases, a high level of predictability is observed from December to April. During the cool phases, the predictability rapidly drops to below normal from November to March. The spring barrier in the atmospheric predictability is therefore a distinct phenomenon for the cold phase, not the warm phase, of the ENSO cycle. The cause of the barrier can be traced to the smaller climate signal and larger climate noise generated during cold events, which in turn can be traced back to the rapidly weakening negative SST anomalies in the tropical Pacific east of the date line. Due to the fact that the signal to noise ratio of this model climate system is very small, an upper bound in atmospheric predictability is present, even when a perfect model atmosphere is considered and large ensemble mean predictions are exploited. The outstanding issues of the dynamical short-term climate prediction employing an atmospheric general circulation model are examined, the current model deficiencies identified, and continuing efforts in model development addressed.

Seasonal and extraseasonal predictions of summer monsoon precipitation by gems(1)

A semi-operational real time short-term climate prediction system has been developed in the Center of Climate and Environment Prediction Research (CCEPRE), Institute of Atmospheric Physics / Chinese Academy of Sciences. The system consists of the following components: the AGCM and OGCM and their coupling, initial conditions and initialization, practical schemes of anomaly prediction, ensemble prediction and its standard deviation, correction of GCM output, and verification of prediction. The experiences of semi-operational real-time prediction by using this system for six years (1989-1994) and of hindeasting for 1980-1989 are reported. It is shown that in most cases large positive and negative anomalies of summer precipitation resulting in disastrous climate events such as severe flood or drought over East Asia can be well predicted for two seasons in advance, although the quantitatively statistical skill scores are only satisfactory due to the difficulty in correctly predicting the signs of small anomalies. Some methods for removing the systematic errors and introducing corrections to the GCM output are suggested. The sensitivity of prediction to the initial conditions and the problem of ensemble prediction are also discussed in the paper.

ADVANCES IN THE MID LATITUDE AIR SEA INTERACTION RESEARCH

In this paper, we reviewed the research condition of the mid latitude air sea interaction and examed the causes of slowly progressing and the main advances for recent 10 years on this project. The results indicated that, the mid latitude ocean plays very important role in world climate changes, the significant signal of mid latitude air sea interaction is the strength of cold air in winter time, and the marine heating anomaly over two strong warm currents region in the northwestern of the Pacific and Atlantic Oceans has important influence on the atmospheric circulation of Northern Hemmisphere both in simultaneous and following seasons (half to one year lag), very strong or very weak marine heating anomaly over Kuroshio and Gulf warm currents in winter may cause the drought or flood atmospheric circulation for the middle and lower reaches of Changjing river in summer. Finally, we proposed that, further exposing the influence of the mid latitude energy system anomaly on the atmospheric circulation and understanding the physical processes are the main objectives of the air sea interaction research, which will be very useful for the short term climate prediction.

THE SPATIAL RESPONSE OF THE CLIMATE SYSTEM TO EXPLOSIVE VOLCANIC ERUPTIONS

Determining the spatial response of the climate system to volcanic forcing is of importance in the development of short-term climate prediction and in the assesment of anthropogenic factors such as global warming. The June 1991 eruption of the Phillippine volcano, Mount Pinatubo, provides an important opportunity to test existing understanding and extend previous emperical analyses of volcanic effect. We identify the spatial climate response to historic eruptions in the surface air temperature and mean-sea- level pressure record and use this information to assess the impact of the Pinatubo eruption. The Pinatubo eruption clearly generated significant global cooling during the years after the event. The magnitude and timing of the cooling is similar to that associated with previous equatorial eruptions. There is good agreement between the spatial patterns of tempurature and circulation anomalies associated with the historic eruptions and those following the Mount Pinatubo event. Evidence of limited higher latitude warming and a major change in the atmospheric circulation is found over the Northern Hemisphere during the first winter after the equatorial eruptions analysed, followed by widespread cooling, but limited change in the atmosphere circulation, during the subsquent 2 years.

THE SPATIAL RESPONSE OF THE CLIMATE SYSTEM TO EXPLOSIVE VOLCANIC ERUPTIONS

Determining the spatial response of the climate system to volcanic forcing is of importance in the development of short-term climate prediction and in the assesment of anthropogenic factors such as global warming. The June 1991 eruption of the Phillippine volcano, Mount Pinatubo, provides an important opportunity to test existing understanding and extend previous emperical analyses of volcanic effect. We identify the spatial climate response to historic eruptions in the surface air temperature and mean-sea- level pressure record and use this information to assess the impact of the Pinatubo eruption. The Pinatubo eruption clearly generated significant global cooling during the years after the event. The magnitude and timing of the cooling is similar to that associated with previous equatorial eruptions. There is good agreement between the spatial patterns of tempurature and circulation anomalies associated with the historic eruptions and those following the Mount Pinatubo event. Evidence of limited higher latitude warming and a major change in the atmospheric circulation is found over the Northern Hemisphere during the first winter after the equatorial eruptions analysed, followed by widespread cooling, but limited change in the atmosphere circulation, during the subsquent 2 years.

Research in China on Climate and its variability

The research program “Dynamical Climatology and the Theory of Short-Term Climate Prediction” supported by the State Committee of Sciences and Technology is introduced. Diagnosis studies on climate variability are summarised. These include the studies on the variability of sea-surface temperature (SST) and its relationship with atmospheric anomalies, on monsoon and seasonal change, and on lowfrequency atmospheric variability.

Some results of applications of statistical method to climate changes and short-term climate prediction in China

Some results of applications of statistical method to climate changes and short-term climate prediction in China

The Monsoon of East Asia and its Global Associations—A Survey

Observations concerning the summer and winter monsoons of East Asia and their global associations are reviewed. The seasonal mean structure, transient variation, including intraseasonal to interannual, and synoptic to planetary scale fluctuations are discussed separately for the two monsoon components. Similarities and differences between the East Asian monsoon and that of India are also surveyed. We also present a description of the current status of monsoon related observational and theoretical research and highlight important scientific problems. The importance of understanding the long-term anomalies of the monsoon is stressed, and an attempt is made to put the East Asian monsoon in a global perspective with a view towards identifying with the problems of long-range weather forecasting or short-term climate prediction, in general. Finally, some future directions of research are suggested.

Short-Term Climate Predictions for Water Management

Abstract Short-term climate predictions (two weeks to two years) have many applications in operation of water supply and flood control facilities. They can influence use of water for irrigation, hydroelectric power production, flood control operation, recreational use of reservoirs, and numerous related water operations. The climate predictions now available have limited usefulness. Their value will increase markedly as ongoing research improves their dependability.

Advances in short term climate prediction

Dynamical and several empirical and statistical approaches to short term climate prediction are surveyed. General circulation models have displayed considerable potential for this application. Physical/synoptic and purely statistical methods have been intensively developed and tested in recent years. Important problems have been recognized in areas such as predictability, forecast verification and evaluation, and combining complementary approaches to prediction.