Mean Temperature Anomalies Research Articles

Equatorial Atlantic sea surface temperature variations: Research note

Abstract Monthly mean sea surface temperature (SST) anomalies were computed for six 10°‐wide boxes stretching across the equatorial Atlantic Ocean for the period 1890–1979. These values were used to produce a time‐longitude section of the interannual SST variability along the equator. This section shows cycles of basin‐wide warming and cooling occurring with irregular periods that typically range between two and four years. The warming and cooling events in these cycles normally display some westward phase propagation. The peak magnitudes of the interannual SST anomalies are generally of the order of 1°C or less, except in the Gulf of Guinea where they can be somewhat larger. An estimate was made of the basin‐wide equatorial SST anomaly in each month (excluding the Gulf of Guinea). This was composited around the times of the warm and cold extremes of the Pacific Southern Oscillation. This analysis revealed a detectable, but rather weak, tendency for phase locking of the interannual SST variations in the e...

Specification of monthly mean surface temperature anomalies in Europe and Asia from concurrent 700 mb monthly mean height anomalies over the Northern Hemisphere

AbstractSpecification equations for the monthly mean air temperature anomalies at 115 surface stations in Eurasia are derived by applying a stepwise forward screening procedure to the simultaneous monthly mean 700 mb height anomalies at 134 grid points in the northern hemisphere and the previous month's local temperature. These equations explain about 65 per cent of the temperature variance by an average of only 4.7 variables, but with marked regional, seasonal and month‐to‐month variations. The main properties of the equations are highlighted by means of several maps and graphs that delineate important spatial and temporal variations.The average properties of the specification equations in the European sector closely resemble those derived previously for North America. However, the results are consistently poorer for stations in Asia, not only for the annual mean, but also during each of the four seasons. Furthermore, the phases of seasonal variation are opposite in Europe and Asia. In both sectors, however, the equations are better in winter than in summer at coastal stations, but the reverse is true at continental stations. The average error in specifying monthly average surface temperature from perfect 700 mb height forecasts should be less than 0.9°C in Europe and 1.2°C in Asia about two‐thirds of the time.

Specification of monthly mean anomalies of surface air temperature in Canada and Alaska

Abstract Anomalies of monthly mean surface temperature observed at 55 stations in Canada and 13 in Alaska from 1951 through 1980 are related to concurrent anomalies of monthly mean 700‐mb height at a network of 107 grid points in North America and the surrounding oceans. The data are screened by a stepwise forward selection procedure to yield multiple regression equations for specifying the monthly mean temperature anomaly at each city and for each month from the field of simultaneous 700‐mb heights plus the previous month's local temperature anomaly. On the average, the specification equations explain 70% of the temperature variance and select as predictors approxiamtely 2 heights to the west of the reference station, 1.5 heights in the vicinity, 1 height to the east, and 0.5 previous temperatures. Most of this paper describes various properties of the specification equations and related atmospheric characteristics on a regional, seasonal and month‐to‐month basis. Five statistical features are mapped for...

Long-Lived Air Temperature Anomalies in the Midlatitudes Forced by the Surface

Abstract A study of long records of monthly mean air temperature (MMAT) for many stations in the Netherlands indicates that the atmosphere's response to surface boundary forcing is often of a very simple local nature. In the Dutch area, the atmosphere seems to respond to a sea surface temperature (SST) anomaly in the North Sea with an air temperature anomaly of the same sign. Because of the abrupt change in lower boundary forcing near the coastline, very small spatial scales are introduced in air temperature anomalies at long time scales. Over the sea MMAT anomalies have much larger time scales than over the land; a similar increase in time scale can be found in the delay of the climatologically normal temperature with respect to the solar forcing. When extended to the United States, the study showed very similar results; that is, monthly mean surface air temperature (MMAT) anomalies live longest in areas where the air temperature response is slowest to the annual cycle in incoming radiation. Apart from b...

A Numerical Case Study of the Development of Large-Scale Thermal Anomalies in the Central North Pacific Ocean

Abstract A 10-level primitive equation ocean circulation model is used to investigate the formation and evolution of large-scale thermal anomalies in the central North Pacific Ocean during the fall and winter of 1976–77. A simplified parameterization of the effects of turbulent vertical mixing produced by wind stirring and surface cooling is included in the model. The numerical experiments consist of prescribed change experiments in which monthly mean ocean temperature anomalies, observed down to 400 m by the North Pacific Experiment (NORPAX), are used to define the prescribed changes (anomalies) in the initial conditions and observed monthly mean anomalies of surface winds, and surface heat fluxes are used to define the prescribed changes in the atmospheric forcing. Oceanic processes are investigated by comparing several prescribed change experiments with observations. With anomalous wind forcing, horizontal advection by anomalous wind-driven surface (Ekman) currents and anomalous wind mixing contribute ...

On the Response of Hemispheric Mean Temperature to Stratospheric Dust: An Empirical Approach

Abstract The cooling effects of stratospheric dust and the corresponding response times for hemispheric mean temperature changes are studied using an empirical approach and a simple time-dependent formulation. The approach couples estimates of stratospheric dust injections by volcanic eruptions to an available record of mean temperature anomalies. The time period examined is 1883–1968. Cooling coefficients (per unit mass of dust) are developed for continued loadings from the transient data; the results are compared to theoretical values developed elsewhere. Response times are also compared. The many uncertainties are noted, as are difficulties introduced by apparent underlying temperature trends. The effort is exploratory in nature, but the overall results are consistent with past arguments that stratospheric dust (as from large volcanic eruptions) is of climatic significance. It is suggested, since climatic changes involve integrals over time, that long-term records of stratospheric dust, as well as othe...

A quasi-biennial standing wave in the Southern Hemisphere and interrelations with sea surface temperature

An empirical orthogonal function analysis is performed on monthly mean sea level pressure (SLP) deviations from normal (anomalies) in the Australasian area and monthly mean sea surface temperature (SST) anomalies in the Tasman Sea for 14 years of data. Only the five components of each that explain most of the variance appear to be significant. Spectral and cross-spectral analysis of the time series of the coefficients reveals significant relations at a quasi-biennial periodicity. An empirical model of the SLP and SST fields for this period is constructed and the amplitudes of the oscillation are found to be about 2 1/2 mb in the monthly mean SLP anomaly field and 0·4 degC in the monthly mean SST anomaly field. Physical and statistical indications are that the SST field is largely caused by the SLP field but some interdependence is present. The quasi-biennial SLP oscillation is related to Pittock's L-index and appears to correspond to a change in wavenumber 3 in the Southern Hemisphere atmospheric circulation. A phase change occurred at the end of 1970, but in even years prior to 1971, and in odd years since 1970, there were increased meridional transports throughout the troposphere and lower stratosphere by the large-scale eddies. A suggestion is made that changes in land–sea heating contrasts may be an important part of the mechanism.

A quasi‐biennial standing wave in the Southern Hemisphere and interrelations with sea surface temperature

AbstractAn empirical orthogonal function analysis is performed on monthly mean sea level pressure (SLP) deviations from normal (anomalies) in the Australasian area and monthly mean sea surface temperature (SST) anomalies in the Tasman Sea for 14 years of data.Only the five components of each that explain most of the variance appear to be significant. Spectral and cross‐spectral analysis of the time series of the coefficients reveals significant relations at a quasi‐biennial periodicity. An empirical model of the SLP and SST fields for this period is constructed and the amplitudes of the oscillation are found to be about 2 1/2 mb in the monthly mean SLP anomaly field and 0·4 degC in the monthly mean SST anomaly field. Physical and statistical indications are that the SST field is largely caused by the SLP field but some interdependence is present.The quasi‐biennial SLP oscillation is related to Pittock's L‐index and appears to correspond to a change in wavenumber 3 in the Southern Hemisphere atmospheric circulation. A phase change occurred at the end of 1970, but in even years prior to 1971, and in odd years since 1970, there were increased meridional transports throughout the troposphere and lower stratosphere by the large‐scale eddies. A suggestion is made that changes in land–sea heating contrasts may be an important part of the mechanism.

Comments on “The Influence of Average Snow Depth on Monthly Mean Temperature Anomaly”

Comments on “The Influence of Average Snow Depth on Monthly Mean Temperature Anomaly”

Further studies of temporal coherence in North Pacific Sea surface temperatures

Temporal coherence between monthly mean space-averaged sea surface temperature anomalies over the North Pacific is appreciably greater than pattern coherence, and thus some conservatism of anomalies as they are redistributed by the North Pacific Ocean gyres is indicated. When they are stratified by initial month, autocorrelations show strong recurrence from one nonsummer month to subsequent months out to 2 years except for summer. The autocorrelations drop between May and June and rise between September and October, changes which appear to be related to wind strength and wind mixing in the oceanic surface layers.

The Influence of Average Snow Depth on Monthly Mean Temperature Anomaly

Abstract Linear regression equations relating monthly mean temperature anomaly to average monthly snow depth and its anomaly were derived for 15 selected stations, using 8 yr of data. It was found that, depending on the characteristics of the station location, from about 10 to 55 percent of the variance of the monthly mean temperature anomaly could be explained in terms of the average monthly snow depth or its anomaly.

Persistent temperature regimes at Kew

AbstractThe 5‐day mean temperature anomalies observed at Kew during the years 1901 to 1961 are examined for evidence of any pattern of variation characteristic of the time of year. It appears that the tendency for the existing temperature regime to persist is weak in spring and autumn, and stronger in winter and summer, being strongest of all in the late summer.

Evolution of monthly mean circulation and weather patterns

Two important conclusions derived from a six‐year experiment in the preparation of monthly mean forecasts are discussed. These are (1) that regardless of how they are made up, monthly mean charts, particularly those constructed for mid‐troposphere levels, to a large extent determine monthly mean temperature and precipitation anomalies; and (2) monthly mean mid‐troposphere flow patterns of the general circulation, when treated on a hemisphere‐wide scale, undergo an orderly evolution and development which can be rationalized at least qualitatively by use of physical and kinematical principles. The second of these conclusions poses vast problems and indeed opens up a new vista for the dynamic meteorologist. Some speculatory hypotheses are suggested.