Showing papers in "Journal of Climate in 1988"
TL;DR: In this article, two stable equilibria have been obtained from a global model of the coupled ocean-atmosphere system developed at the Geophysical Fluid Dynamics Laboratory of NOAA.
Abstract: Two stable equilibria have been obtained from a global model of the coupled ocean-atmosphere system developed at the Geophysical Fluid Dynamics Laboratory of NOAA. The model used for this study consists of general circulation models of the atmosphere and the world oceans and a simple model of land surface. Starting from two different initial conditions, “asynchronous” time integrations of the coupled model, under identical boundary conditions, lead to two stable equilibria. In one equilibrium, the North Atlantic Oman has a vigorous thermohaline circulation and relatively saline and warm surface water. In the other equilibrium, there is no thermohaline circulation, and an intense halocline exists in the surface layer at high latitudes. In both integration the, air-sea exchange of water is adjusted to remove a systematic bias of the model that surpresses the thermohaline circulation in the North Atlantic. Nevertheless these results raise the intriguing possibility that the coupled system may have a...
889 citations
TL;DR: In this paper, a global monthly sea surface temperature analysis is described which uses real-lime in situ (ship and buoy) and satellite data and combines the advantages of both types of data: the ground truth of in situ data and the improved coverage of satellite data.
Abstract: A global monthly sea surface temperature analysis is described which uses real-lime in situ (ship and buoy) and satellite data. The method combines the advantages of both types of data: the ground truth of in situ data and the improved coverage of satellite data. The technique also effectively eliminates most of the bias differences between the in situ and satellite data. Examples of the method are shown to illustrate these points. Sea surface temperature (SST) data from quality-controlled drifting buoys are used to develop error statistics for a 24-month period from January 1985 through December 1986. The average rms monthly error is 0.78°C; the modulus of the monthly blasts (i.e., the average of the absolute value of the monthly biases) is 0.09°C.
794 citations
TL;DR: In this article, several equations were developed that related the effect of urban growth, measured by increasing population, to the mean seasonal and annual temperature: the diurnal maximum, minimum, average, and range.
Abstract: Several equations were developed that related the effect of urban growth, measured by increasing population, to the mean seasonal and annual temperature: the diurnal maximum, minimum, average, and range. These equations were derived from a network of 1219 stations across the United States, which were analyzed for the years 1901–84. The results indicate that urban effects on temperature are detectable even for small towns with populations under 10 000. Stations with populations near 10 000 are shown to average 0.1°C warmer for the mean annual temperature than nearby stations located in rural areas with populations less than 2000. Urbanization decreases the daily maxima in all seasons except winter and the temperature range in all seasons. It increases the diurnal minima and the daily means in all seasons. The equations indicate that, for the annual mean temperature, urbanization during the twentieth century accounts for a warm bias of about 0.06°C in the U.S. Historical Climatology Network (HCN). ...
616 citations
TL;DR: In this article, the temporal variability of model soil moisture and precipitation have been studied in an effort to understand the interactions of these variables with other components of the climate system, and it has been shown that the spectra of monthly mean precipitation over land are close to white at all latitudes, with total variance decreasing poleward.
Abstract: An atmospheric general circulation model with prescribed sea surface temperature and cloudiness was integrated for 50 years in order to study atmosphere-land surface interactions. The temporal variability of model soil moisture and precipitation have been studied in an effort to understand the interactions of these variables with other components of the climate system. Temporal variability analysis has shown that the spectra of monthly mean precipitation over land are close to white at all latitudes, with total variance decreasing poleward. In contrasts, the spectra of soil moisture are red, and become more red with increasing latitude. As a measure of this redness, half of the total variance of a composite tropical soil moisture spectrum occurs at periods longer than nine months, while at high latitudes, half of the total variance of a composite soil moisture spectrum occurs at periods longer than 22 months. The spectra of soil moisture also exhibit marked longitudinal variations. These spectral...
448 citations
TL;DR: The first year-round observations available for any site in Taylor Valley are reported in this article, where the mean annual solar flux at Lake Hoare was 92 W/sq m during 1986, the mean air temperature -17.3 C, and the mean 3m wind speed 3.3 m/s.
Abstract: In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, the first year-round observations available for any site in Taylor Valley are reported. The mean annual solar flux at Lake Hoare was 92 W/sq m during 1986, the mean air temperature -17.3 C, and the mean 3-m wind speed 3.3 m/s. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year.
343 citations
TL;DR: In this paper, the authors examined annual variations in African rainfall using rotated principal component analysis (PCA) applied to anomalies from the annual mean as well as seasonal anomalies, and found that the dominant features of year-to-year variations of African rainfall appear to be the high spatial coherence of rainfall anomalies over large portions of the continent and several dipole regions, that are adjacent regions which tend to experience rainfall anomalies of opposite sign, are found and discussed.
Abstract: Interannual variations in African rainfall are examined using rotated principal component analysis (PCA) applied to anomalies from the annual mean as well as seasonal anomalies. The rotated PCA loading patterns suggest several “preferred” continental-scale rainfall anomaly patterns. The dominant features of year-to-year variations in African rainfall appear to be the high spatial coherence of rainfall anomalies over large portions of the continent. In addition, several dipole regions, that is, adjacent regions which tend to experience rainfall anomalies of opposite sign, are found and discussed. One dipole region, the sub-Saharan region, appears to have a relationship with a characteristic Atlantic sea surface temperature anomaly pattern during boreal summer. During austral summer, the tendency for a large-scale dipole pattern in southeast Africa is apparent, as is an association of this pattern with the warm and cold phases of the El Nin/Southern Oscillation (ENSO) phenomenon. Normalized rainfal...
296 citations
TL;DR: A physically based ground hydrology model is developed to improve the land-surface sensible and latent heat calculations in global climate models as discussed by the authors, where the processes of transpiration, evaporation from intercepted precipitation and dew, evapping from bare soil, infiltration, soil water flow, and runoff are explicitly included in the model.
Abstract: A physically based ground hydrology model is developed to improve the land-surface sensible and latent heat calculations in global climate models (GCMs). The processes of transpiration, evaporation from intercepted precipitation and dew, evaporation from bare soil, infiltration, soil water flow, and runoff are explicitly included in the model. The amount of detail in the hydrologic calculations is restricted to a level appropriate for use in a GCM, but each of the aforementioned processes is modeled on the basis of the underlying physical principles. Data from the Goddard Institute for Space Studies (GISS) GCM are used as inputs for off-line tests of the ground hydrology model in four 8° × 10° regions (Brazil, Sahel, Sahara, and India). Soil and vegetation input parameters are calculated as area-weighted means over the 8° × 10° gridhox. This compositing procedure is tested by comparing resulting hydrological quantities to ground hydrology model calculations performed on the 1° × 1° cells which co...
282 citations
TL;DR: In this paper, the hemispheric mean land-surface air temperature series developed for both hemispheres by Jones et al. are updated through 1987 and the global temperature estimate for 1987 is the third warmest on record.
Abstract: The hemispheric mean land-surface air temperature series developed for both hemispheres by Jones et al. are updated through 1987. The global temperature estimate for 1987 is the third warmest on record, 1858–1987. Recent warming over the last 20 years (1967–86) is shown to be centered on middle latitude belts in both hemispheres.
259 citations
TL;DR: In this paper, an analysis has been made of variations in the atmospheric circulation with periods of more than 50 days occurring in the Southern Hemisphere between 1980 and 1986, using analyses produced by the European Centre for Medium Range Weather Forecasts (ECMWF), mainly at the 500 hPa level.
Abstract: An analysis has been made of variations in the atmospheric circulation with periods of more than 50 days occurring in the Southern Hemisphere between 1980 and 1986, using analyses produced by the European Centre for Medium Range Weather Forecasts (ECMWF), mainly at the 500 hPa level. A smoothed mean annual cycle was removed from the data to define anomalies which were then filtered to retain variations with periods greater than 50 days. The >50 day period variations account for 20%–30% of the variance of daily 500 hPa geopotential anomalies at midlatitudes, up to 50% over Antarctica and more than 70% in the tropics. The total variance was found to be more uniform at high latitudes over the southern oceans than reported in previous studies, possibly reflecting the more comprehensive dataset used in the ECMWF analyses. The first three empirical orthogonal functions (EOFs) of the geopotential height anomalies amounted for 40% of the low-pass filtered fields. The first is a zonal field with the sign ...
213 citations
TL;DR: In this article, an analysis of sea surface temperature (SST) fluctuations in the upwelling region along the Benguela coat and its relationship to rainfall variability both along the coast and throughout equatorial and southern Africa is presented.
Abstract: This article presents the results of an analysis of sea surface temperature (SST) fluctuations in the upwelling region along the Benguela coat and its relationship to rainfall variability both along the coast and throughout equatorial and southern Africa. The analysis incorporates compositing and time series analysis. Coastal rainfall is markedly enhanced during warm-water years and suppressed during cold-water years. The effects are strongest in March and April; at some stations, March totals of 50 mm in cold-water years contrast with 200 to 400 mm in March of warm-water years. Spectral analysis shows the variability of SSTs to be more pronounced on time scales of 5 to 6 years, and strong relationships with rainfall throughout equatorial and southern Africa are evident on this time scale. In coastal regions there may be some degree of direct local forcing of rainfall anomalies via SST anomalies, but the temporal and geographical patterns of the relationships suggest that in general, both SSTs an...
203 citations
TL;DR: In this article, the variations and trends in tropospheric and low-stratospheric temperature for seven climatic zones, hemispheres, and world for intervals 1958-87 and 1973-87, based on 63 well-distributed radiosonde stations.
Abstract: Examined in this paper are the variations and trends in tropospheric and low-stratospheric temperature for seven climatic zones, hemispheres, and world for intervals 1958–87 and 1973–87, based on 63 well-distributed radiosonde stations. For the 30-yr interval 1958–87, these data indicate an increase in year-average global temperature at the surface and in the tropospheric 850–300 mb layer of 0.08°C (10 yr)−1 and 0.09°C (10 yr)−1, respectively, just significant at the 5% level. Nevertheless during this interval there is evidence for a slight decrease in year-average temperature at the surface and in the troposphere of the north polar and north temperate zones. The global 300–100 mb temperature is indicated as having decreased by 0.18°C (10 yr)−1 during this 30-yr interval (significant at the 1% level), with a temperature decrease in all seven climatic zones, though largest in the south polar zone (associated with the Antarctic “ozone hole” phenomenon). For the 15-yr interval 1973–87, the global te...
TL;DR: The time and spatial variation of the Southern Hemisphere 500 hPa zonal wind has been examined using spectral analysis, bandpass filtering, and empirical orthogonal function (EOF) analysis applied to a 15-year sample of Australian hemispheric analyses.
Abstract: The time and spatial variation of the Southern Hemisphere 500 hPa zonal wind has been examined using spectral analysis, bandpass filtering, and empirical orthogonal function (EOF) analysis applied to a 15-year sample of Australian hemispheric analyses. Spectral analysis of the entire 15-year record of the 500 hPa zonal mean westerly wind shows significant peaks only on the seasonal and interannual time scales. The mean segmented spectra for each season failed to show any additional significant peaks at higher frequencies or any significant differences between seasons. The primary pattern of variation revealed by EOF analysis shows similar behavior on synoptic to seasonal time scales, with compensating departures occurring at intervals of 20° latitude. The first EOF has opposing peaks near 40° and 60°S and shows an equivalent barotropic pattern when correlated with individual grid point values at 500 hPa and mean sea level pressure. Correlations of the zonal pattern with regional anomalies reveal ...
TL;DR: In this article, the atmospheric 700 mb height anomalies associated with high persistence SST cases indicate that strong SST persistence is associated with long-lasting atmospheric anomaly patterns, and for highly persistent January SST anamalies, 700mb anomalies often last from December through February.
Abstract: North Pacific monthly sea surface temperature (SST) anomalies are more persistent than a first-order Markev process, often lasting for more than 5 months. Sea surface temperature persistence undergoes an annual cycle that is attributable to the depth of the surface mixed layer and to the annual cycle of focing. For a given lag, the pattern correlation is minimum when it involves SST during the summer months and maximum when it involves SST during the winter months. Average winter SST anomalies that have exhibited greatest persistence during the last four decades have been negative in the central North Pacific and positive along the West Coast but antipersistent SST anomalies have not confermed to a repeated pattern. The atmospheric 700 mb height anomalies associated with high persistence SST cases indicate that strong SST persistence is associated with long-lasting atmospheric anomaly patterns. For highly persistent January SST anamalies, 700 mb anomalies often last from December through February...
TL;DR: The most effective procedure for diurnal heating is the "force-restore" approach as mentioned in this paper, which uses a prognostic equation for temperature that reproduces exactly the response to periodic heating and uniform thermal properties.
Abstract: Atmospheric general circulation models require efficient approximation procedures for including the vertical diffusion or heat into an underlying soil. The most effective procedure for diurnal heating—the “force-restore” approach—uses a prognostic equation for temperature that reproduces exactly the response to periodic heating and uniform thermal properties. Errors result from the neglect of higher harmonies in time in the forcing and from inhomogeneous thermal properties of the underlying soil. Neglect of higher harmonics is tolerable, in part because the response decreases with an increased forcing frequency. Neglect of vertical variation of thermal conductivity and specific heat can introduce major errors in the force-restore treatment, a possibility illustrated by the response to diurnal periodic surface forcing with a snow layer overlying a soil layer. A generalization of the force-restore procedure is developed for inhomogeneous thermal properties and illustrated for a snow layer overlying...
TL;DR: In this article, the authors found a correlation between the 700-mb height on the Northern Hemisphere and the solar flux on the Southern Hemisphere, and interpreted this similarity as a correlation of point-to-point correlations between the height at selected points and the heights at all other points.
Abstract: Sea level pressure, surface air temperature, and 700-mb temperature and geopotential height show a probable association with the 11-year solar cycle which can be observed only if the data are divided according to the phase of the Quasi-Biennial Oscillation. The range of the response is as large as the interannual variability of the given element, and the correlations prove statistically meaningful when tested by Monte Carlo techniques. The sign of the correlations changes over the hemisphere on the spatial scale of extensive teleconnections. The correlations at 700 mb tend to be of opposite sign in the east and west years of the QBO, a result which Labitzke and van Loon also found in an analysis of the stratosphere. The pattern of correlation between the 700-mb heights on the Northern Hemisphere and the solar flux is the same as that of point-to-point correlations (teleconnections) between the 700-mb height at selected points and the heights at all other points. We interpret this similarity as a ...
TL;DR: In this article, a selected group of nine climate-sensitive tree-ring chronologies from old post oak trees are used to reconstruct the June Palmer Drought Severity Index (PDSI) from 1698 to 1980 for two large regions in northern and southern Texas.
Abstract: A selected group of nine climate-sensitive tree-ring chronologies from old post oak trees are used to reconstruct the June Palmer Drought Severity Index (PDSI) from 1698 to 1980 for two large regions in northern and southern Texas. Analysis of tree growth and monthly climate variables indicate that the June PDSI is the most robust climate signal evident in these chronologies, and principal component analysis (PCA) reveals a north-south geographic pattern in the relationships between the regional tree-ring time series. Serially random amplitude series from the first two significant eigenvectors of tree growth, which explain 65% of the total variance in the tree-ring data, were entered into stepwise multiple regression as predictors of regionally averaged June PDSI in north and south Texas for the common interval 1931–80. The regression models explain 59% and 60% of the variance in north and south Texas June PDSI, respectively, and both reconstructions are well verified against independent June PDS...
TL;DR: In this paper, experiments with climate models reveal regional soil moisture changes over North America when carbon dioxide is doubled (or the equivalent radiation perturbation due to an increase in all the “greenhouse gases” takes place).
Abstract: In anticipation of a global warming in the decades ahead due to an increased greenhouse effect from infrared-absorbing trace gases, it is not too early to enquire what this may mean in terms of changes in patterns of precipitation and soil moisture. These patterns are a secondary result of the temperature distribution and are therefore difficult to specify, but the practical importance attached to any regional changes in soil moisture is obviously enormous. In this study we have attempted to see how experiments with climate models reveal regional soil moisture changes over North America when carbon dioxide is doubled (or the equivalent radiation perturbation due to an increase in all the “greenhouse gases” takes place). Results from five of the current state of the art climate models are compared with each other and with existing estimates of soil moisture distribution, with emphasis on how they respond to the carbon dioxide perturbation. (The models are those of GFDL, GISS, NCAR, OSU, and UKMO.)...
TL;DR: In this paper, an improved version of the Nimbus-7 cloud retrieval algorithm was validated using data from Nimbus 7 Temperature Humidity Infrared Radiometer and Total Ozone Mapping Spectrometer.
Abstract: An improved version of the Nimbus-7 cloud retrieval algorithm was validated using data from Nimbus-7 Temperature Humidity Infrared Radiometer and Total Ozone Mapping Spectrometer to determine cloudiness parameters for the globe. Quantitative validation of total cloud amount was performed by comparing the algorithm results with estimates derived from GOES images and auxiliary meteorological data. The systematic errors of the Nimbus-7 total cloud-amount algorithm, relative to the GOES-derived estimates, were found to be less than 10 percent. The random errors of daily estimates ranged between 7 and 16 percent, day or night.
TL;DR: In this article, seasonal and annual (July through June) precipitation data for up to 197 stations are used to analyze variability in the High/Dry (H/D) and Low/Wet (L/W or warm event) modes of the Southern Oscillation (SO) over the tropical Americas and the Caribbean Islands to 30°S latitude.
Abstract: Seasonal and annual (July through June) precipitation data for up to 197 stations are used to analyze variability in the High/Dry (H/D) and Low/Wet (L/W or warm event) modes of the Southern Oscillation (SO) over the tropical Americas and the Caribbean Islands to 30°S latitude. Precipitation is significantly higher during H/D events than during L/W in northern summer, autumn and winter at most stations in the southern Caribbean and northern South America including the northern Andes and Amazon River basin. Precipitation is, in general, significantly higher in L/W than in H/D modes at higher subtropical latitudes of both hemispheres, especially in northern autumn and winter over the southern United States, Cuba and Mexico, and in spring and autumn over southern Brazil, Paraguay and Argentina. A similar pattern of spatial precipitation variability occurs in the July–June data and significant H/D minus L/W precipitation differences are found at one-third of the stations. Although drought occurs in No...
TL;DR: In this paper, the statistical relationship between monthly precipitation (P) and shallow groundwater levels (GW) in 20 wells scattered across Illinois with data for 1960-84 were defined using autoregressive integrated moving average (ARIMA) modeling.
Abstract: The statistical relationships between monthly precipitation (P) and shallow groundwater levels (GW) in 20 wells scattered across Illinois with data for 1960–84 were defined using autoregressive integrated moving average (ARIMA) modeling. A lag of 1 month between P to GW was the strongest temporal relationship found across Illinois, followed by no (0) lag in the northern two-thirds of Illinois where mollisols predominate, and a lag of 2 months in the alfisols of southern Illinois. Spatial comparison of the 20 P-GW correlations with several physical conditions (aquifer types, soils, and physiography) revealed that the parent soil materials of outwash alluvium, glacial till, thick loess (≥2.1 m), and thin loess (>2.1) best defined regional relationships for drought assessment. Equations developed from ARTMA using 1960–79 data for each region were used to estimate GW levels during the 1980–81 drought, and estimates averaged between 25 to 45 cm of actual levels. These estimates are considered adequate...
TL;DR: In this article, a linearized, steady state, primitive equation model is used to simulate the climatological zonal asymmetries (stationary eddies) in the wind and temperature fields of the 18 000 YBP climate during winter.
Abstract: A linearized, steady state, primitive equation model is used to simulate the climatological zonal asymmetries (stationary eddies) in the wind and temperature fields of the 18 000 YBP climate during winter We compare these results with the eddies simulated in the ice age experiments of Broccoli and Manabe, who used CLIMAP boundary conditions and reduced atmospheric CO2 in an atmospheric general circulation model (GCM) coupled with a static mixed layer ocean model The agreement between the models is good, indicating that the linear model can be used to evaluate the relative influences of orography, diabatic heating, and transient eddy heat and momentum transports in generating stationary waves We find that orographic forcing dominates in the ice age climate The mechanical influence of the continental ice sheets on the atmosphere is responsible for most of the changes between the present day and ice age stationary eddies This concept of the ice age climate is complicated by the sensitivity of t
TL;DR: In this article, the authors examined the seasonal variations in cyclone and anticyclone frequencies, mean cyclone pressures and other cyclone characteristics in the Arctic basin from 70°-907deg;N for the period 1979-85, using improved pressure analyses incorporating data from a network of drifting buoys.
Abstract: Synoptic activity in the Arctic basin from 70°–907deg;N is examined for the period 1979–85, using improved pressure analyses incorporating data from a network of drifting buoys. Geographical and seasonal variations in cyclone and anticyclone frequencies, mean cyclone pressures and other cyclone characteristics are determined. Results, in general, compare favorably with those from earlier studies. The atmospheric circulation of the Arctic is characterized by strong seasonality, but with considerable year-to-year variability, evidenced through large-scale seasonal shifts in the position and intensity of cyclone and anticyclone frequency maxima, the types of systems comprising these pattern, and major cyclone tracks. In winter and spring, cyclonic activity is largely restricted to the eastern Arctic. Local frequency maxima are found near Svalbard, the northern tip of Novaya Zemlya, and, in winter, also near the Pole at about 90°E. The systems comprising these patterns are migratory, the majority ent...
TL;DR: In this paper, a technique is presented for estimating the ground-surface sun-synchronous satellite data using only satellite data, which is tested by comparing the results from year-long satellite data sets with simultaneous ground-measured measurements taken at five continental United States sites.
Abstract: A technique is presented for estimating insolation at the earth's surface using only sun-synchronous satellite data. The technique was tested by comparing the insolation results from year-long satellite data sets with simultaneous ground-measured insolation taken at five continental United States sites. Monthly average insolation values derived from the satellite data showed a standard error of 4.2 W/sq m, or 2.7 percent of the average ground insolation value.
TL;DR: In this article, the authors compared the performance of GFDL, GISS, NCAR, OSU and UKMO models over North America and found that the largest scale features were generally simulated quite well.
Abstract: This is a sequel to a comparative study of the performance of five climate models over North America; here we investigate their performance over the region most directly under the influence of the Asian monsoon (taken to be equator to 60°N, 60° to 140°E). Emphasis is on soil moisture, since it is a difficult parameter to calculate and therefore provides a severe test of the climate models. Furthermore, soil moisture is a quantity of considerable concern to agriculture and the management of ecological systems generally. The five models compared were those of GFDL, GISS, NCAR, OSU and UKMO. While there were many significant differences in detail between the soil moisture distributions produced by the various control runs for winter and for summer, and also between the model climates and the observed climate of the region, the largest scale features were generally simulated quite well. These features are a considerably drier average climate in the northern part of our region compared to the southern...
TL;DR: In this paper, the relationship between mean rainfall and the relative variability of annual rainfall is shown to be different for stations that have consistent relationships with ENSO compared with stations not affected by it.
Abstract: The relationship between mean rainfall and the relative variability of annual rainfall is shown to be different for stations that have consistent relationships with ENSO compared with stations not affected by ENSO. Variability is typically one-third to one-half higher for ENSO-affected stations. It appears that ENSO causes a snore variable climate in the areas it affects.
TL;DR: In this paper, the authors used METEOSAT infrared and water vapor radiance data from the ISCCP dataset to describe climatic characteristics for the months of July 1983, 1984 and 1985, corresponding to very different rainy seasons in Sahelian Africa.
Abstract: METEOSAT infrared and water vapor radiance data from the ISCCP dataset are used to describe climatic characteristics for the months of July 1983, 1984 and 1985, corresponding to very different rainy seasons in Sahelian Africa. Mean cloudiness distribution diurnal cycle of local convection, life cycle of squall lines and drift velocities computed from WV images are studied. The results and their interannual variations are shown to be consistent with analyses from other data sources, including conventional data. The utilization of both kinds of analyses allows not only the validation of the satellite approach but also an improved description of the climatic situations as different parameters are inferred. The main cloud systems and circulation differences between the driest and the wettest months studied are in general agreement with previous observational and simulation studies comparing dry and wet years.
TL;DR: In this article, several series of 30-day simulations with a global simulation model are used to evaluate the sensitivities to continental snow cover over North America and Eurasia. The model is initialized with National Meteorological Center analyses for specific dates during the winter of 1976/77 through 1983/84, and snow cover in each case is prescribed according to the distribution derived from observational data; and the distribution containing a corresponding anomaly of the opposite sign.
Abstract: Several series of 30-day simulations with a global simulation model are used to evaluate the sensitivities to continental snow cover over North America and Eurasia. The model is initialized with National Meteorological Center analyses for specific dates during the winter of 1976/77 through 1983/84, and snow cover in each case is prescribed according to 1) the distribution derived from observational data; and 2) the distribution containing a corresponding anomaly of the opposite sign. In ten pairs of midwinter forecasts, the major effect of extensive snow cover in eastern North America is a reduction of the near-surface air temperature in the vicinity of the snow anomaly. When snow cover is extensive, sea level pressures are somewhat lower and precipitation amounts somewhat higher offshore of the East Coast; sea level pressures are generally higher inland. In a set of six March cases, positive anomalies of Eurasian snow cover reduce the air temperatures by at least several degrees ceisius througho...
TL;DR: The authors examined the relationship between atmospheric pressure at Darwin, Tahiti and Santiago and indices of the Southern Oscillation (SO) formed from these pressures for the period 1883-1984, and the sea surface temperature in the eastern equatorial Pacific (SST*) as well as Indian summer-monsoon rainfall and continental and marine hemispheric temperatures.
Abstract: Relationships are examined among records of atmospheric pressure at Darwin, Tahiti and Santiago and indices of the Southern Oscillation (SO) formed from these pressures for the period 1883–1984, and the sea surface temperature in the eastern equatorial Pacific (SST*) as well as Indian summer-monsoon rainfall and continental and marine hemispheric temperatures. In general, the correlations of pressures and SO indices with SST* have been greatest since World War II, but were also relatively high prior to World War I. An exception is Tahiti pressure which is poorly correlated with SST* until about 1940. The correlations have tended to be higher when moderate or strong El Nino were most frequent. The question is discussed whether the decrease in correlations among the various datasets that is apparent in the middle third of the time period in question, roughly from 1920 to 1950, reflects a real change in atmospheric processes or is due to data problems. It is suggested that prior to World War I the p...
TL;DR: In this paper, the NASA Goddard Institute for Space Studies model was used to investigate radiative, dynamical and regional sensitivities to model grid size, and the results showed that model resolution affected two key processes in the control runs, moist convection and the nonlinear transfer of kinetic energy into the zonal mean flow.
Abstract: Climate change simulations run with two different resolutions (8 deg by 10 deg and 4 deg by 5 deg) of the NASA Goddard Institute for Space Studies model are used to investigate radiative, dynamical, and regional sensitivities to model grid size. The results show that model resolution affected two key processes in the control runs, moist convection and the nonlinear transfer of kinetic energy into the zonal mean flow. It was found that the finer resolution model has more penetrative convection but less convection overall, with the results that its temperature and wind structure were altered with respect to the coarser grid model.
TL;DR: In this paper, a scheme for the automated classification of oceanic cloud patterns is presented for the detection of directional patterns (cloud “streets or rolls) and open cells, based on the assumption of multinormal distributions of the features, a simple classification algorithm is developed.
Abstract: A scheme is presented for the automated classification of oceanic cloud patterns. The 20 cloud classes reflect the rich variety of morphologies that are detectable from space. A training set is defined by 2000 samples of size 128 × 128 km taken from GOES visible and infrared images over the western Atlantic in February 1984. Class discrimination is obtained from 13 features representing height, albedo, shape and multilayering characteristics of the cloud fields. Two features derived from the two-dimensional power spectrum of the visible images proved essential for the detection of directional patterns (cloud “streets or rolls) and open cells. Based on the assumption of multinormal distributions of the features, a simple classification algorithm is developed. The generation of artificial samples yields a theoretical separability of 97% while the actual separability obtained on the training set is 95%. From 1020 independent samples, the separate verification of three expert nephanalysts indicates s...