Search Results
You are looking at 1 - 10 of 11 items for
- Author or Editor: Carl O. Erickson x
- Refine by Access: All Content x
Abstract
Hemispheric composites of 700 mb height during each of four unusually warm summers in the contiguous United States show a characteristic “3-wave” pattern of anticyclonic anomalies over the eastern North Pacific, the United States and the North Atlantic. Other common features are an anticyclonic anomaly over eastern Russia and mostly above-normal heights for the entire Northern Hemisphere north of 15°N, especially over subtropical and lower middle latitudes. For tour unusually cool summers, generally inverse composite patterns are noted. Sea level pressure composites for those warm and cool summers show similar, but less well defined, anomalies.
More generally, based on 33 years of data and Monte Carlo testing procedures, there appears to be a statistically significant lagged relation between zonally averaged 700 mb height anomalies at lower latitudes of the Northern Hemisphere and subsequent mean summer temperatures in the United States. Relations from sector-averaged anomalies are mostly inferior to those from hemispheric zonal averages. Correlations of lesser significance exist between zonally averaged 700 mb height anomalies at middle and high latitudes and subsequent mean summer temperatures.
Abstract
Hemispheric composites of 700 mb height during each of four unusually warm summers in the contiguous United States show a characteristic “3-wave” pattern of anticyclonic anomalies over the eastern North Pacific, the United States and the North Atlantic. Other common features are an anticyclonic anomaly over eastern Russia and mostly above-normal heights for the entire Northern Hemisphere north of 15°N, especially over subtropical and lower middle latitudes. For tour unusually cool summers, generally inverse composite patterns are noted. Sea level pressure composites for those warm and cool summers show similar, but less well defined, anomalies.
More generally, based on 33 years of data and Monte Carlo testing procedures, there appears to be a statistically significant lagged relation between zonally averaged 700 mb height anomalies at lower latitudes of the Northern Hemisphere and subsequent mean summer temperatures in the United States. Relations from sector-averaged anomalies are mostly inferior to those from hemispheric zonal averages. Correlations of lesser significance exist between zonally averaged 700 mb height anomalies at middle and high latitudes and subsequent mean summer temperatures.
Abstract
Zonally averaged composite anomalies of 700 mb height for years preceding and during four warm winters in the contiguous United States show generally positive anomalies over subtropical and middle latitudes and generally negative anomalies over high latitudes. The overall composite hemispheric height anomaly was positive for the years with warm winters. For four years with cold winters, generally inverse composite patterns are noted. In both composites, pattern reversals with respect to latitude occur during the following spring seasons. The four warm and four cold winters were those whose average temperature anomalies, nationwide, were the largest in the 33-yeu period 1948–80. The occurrence of consecutive severe winters within this relatively short record places limits on interpretation.
More generally, based on 33 years of data and Monte Carlo testing procedures, a statistical relation that is marginally significant at the 95% level appears to exist between the overall pattern of zonally averaged 700 mb height anomalies and mean winter temperatures in the United States. The relation is weaker and less coherent than that previously found with respect to mean summer temperatures. However, as with summer, the individual coefficients that are statistically significant are overwhelmingly positive in sign.
The overall correlation patterns with respect to spring and fall mean temperatures in the United States are obviously not significant. In terms of area-weighted percentages, the totals of individually significant coefficients for spring and fall are even less than to be expected from chance.
Abstract
Zonally averaged composite anomalies of 700 mb height for years preceding and during four warm winters in the contiguous United States show generally positive anomalies over subtropical and middle latitudes and generally negative anomalies over high latitudes. The overall composite hemispheric height anomaly was positive for the years with warm winters. For four years with cold winters, generally inverse composite patterns are noted. In both composites, pattern reversals with respect to latitude occur during the following spring seasons. The four warm and four cold winters were those whose average temperature anomalies, nationwide, were the largest in the 33-yeu period 1948–80. The occurrence of consecutive severe winters within this relatively short record places limits on interpretation.
More generally, based on 33 years of data and Monte Carlo testing procedures, a statistical relation that is marginally significant at the 95% level appears to exist between the overall pattern of zonally averaged 700 mb height anomalies and mean winter temperatures in the United States. The relation is weaker and less coherent than that previously found with respect to mean summer temperatures. However, as with summer, the individual coefficients that are statistically significant are overwhelmingly positive in sign.
The overall correlation patterns with respect to spring and fall mean temperatures in the United States are obviously not significant. In terms of area-weighted percentages, the totals of individually significant coefficients for spring and fall are even less than to be expected from chance.
Abstract
No abstract available.
Abstract
No abstract available.
PICTURE OF THE MONTH
A jet Stream Cirrus Shield
Abstract
No abstract available.
Abstract
No abstract available.
Abstract
An area of disturbed weather over the Bahamas is studied in detail for the 3-day period, Aug. 9–11, 1966. The coupling of an upper level cold-core cyclone with an approaching low-level wave was largely responsible for the considerable increase in cloudiness and weather observed on August 9 and 10.
Warm anomalies in the lower stratosphere were even larger than the cold anomalies of the upper troposphere, strongly suggesting the existence of large-scale vertical motions at both levels.
Results from a diagnostic numerical model show that the Laplacian of thermal advection was the single most important forcing function contributing to tropospheric vertical motion. Agreement between observed cloudiness and calculated vertical motion was generally good.
Abstract
An area of disturbed weather over the Bahamas is studied in detail for the 3-day period, Aug. 9–11, 1966. The coupling of an upper level cold-core cyclone with an approaching low-level wave was largely responsible for the considerable increase in cloudiness and weather observed on August 9 and 10.
Warm anomalies in the lower stratosphere were even larger than the cold anomalies of the upper troposphere, strongly suggesting the existence of large-scale vertical motions at both levels.
Results from a diagnostic numerical model show that the Laplacian of thermal advection was the single most important forcing function contributing to tropospheric vertical motion. Agreement between observed cloudiness and calculated vertical motion was generally good.
Abstract
Hurricane Dorothy, July 1966, possessed both extratropical and tropical features. A number of factors contributed to storm development, including a well-defined pre-existing disturbance, high-level advection of vorticity and kinetic energy, baroclinicity of both the extratropical and tropical-storm types, and a moderate degree of latent instability.
Abstract
Hurricane Dorothy, July 1966, possessed both extratropical and tropical features. A number of factors contributed to storm development, including a well-defined pre-existing disturbance, high-level advection of vorticity and kinetic energy, baroclinicity of both the extratropical and tropical-storm types, and a moderate degree of latent instability.
Abstract
Several TIROS photographs of cumulonimbus clouds and thunderstorms over the Florida area are compared with synoptic surface and upper-wind data. The orientations of the cirrus anvils of well-developed clouds generally show good directional agreement with the existing vertical wind shears between the lower and upper troposphere. Limited evidence also suggests that the length and character of the anvils may sometimes be used as qualitative indicators of shear magnitude, the longer and more pronounced anvils being positively correlated with stronger vertical shear.
In agreement with earlier studies, it is found that cumulonimbus clouds often appear as relatively small or medium-sized, irregular, bright masses in TIROS pictures, hence such clouds often can be tentatively identified from their picture appearance alone. Such identification is still largely a subjective procedure. The anvils of well-developed cumulonimbi, when attached to the parent cloud, are rather distinctive and are an aid to identification.
A few TIROS pictures of the Florida area under relatively clear conditions are shown for comparative purposes. The problems arising from specular reflection and from variations in overall photo appearance resulting from changing camera angle are briefly discussed.
Abstract
Several TIROS photographs of cumulonimbus clouds and thunderstorms over the Florida area are compared with synoptic surface and upper-wind data. The orientations of the cirrus anvils of well-developed clouds generally show good directional agreement with the existing vertical wind shears between the lower and upper troposphere. Limited evidence also suggests that the length and character of the anvils may sometimes be used as qualitative indicators of shear magnitude, the longer and more pronounced anvils being positively correlated with stronger vertical shear.
In agreement with earlier studies, it is found that cumulonimbus clouds often appear as relatively small or medium-sized, irregular, bright masses in TIROS pictures, hence such clouds often can be tentatively identified from their picture appearance alone. Such identification is still largely a subjective procedure. The anvils of well-developed cumulonimbi, when attached to the parent cloud, are rather distinctive and are an aid to identification.
A few TIROS pictures of the Florida area under relatively clear conditions are shown for comparative purposes. The problems arising from specular reflection and from variations in overall photo appearance resulting from changing camera angle are briefly discussed.
Abstract
Satellite photographs have revealed the occasional existence of broad and extensive cloud bands reaching from tropical storms northeastward into the westerlies of middle latitudes. Fourteen well-defined cases of such cloud connections from western North Pacific tropical storms in the autumns of 1967, 1968 and 1969 are examined with respect to the large-scale circulation. The composited data show that the 300-mb westerlies over the North Pacific increase for several days following the onset of the cloud-band connections. Hemispheric kinetic energy for the whole troposphere tends to increase in similar fashion. These associations suggest that the injection of heat and moisture from tropical cyclones into the middle latitudes plays a significant role in the autumnal buildup of the planetary-scale circulation.
Abstract
Satellite photographs have revealed the occasional existence of broad and extensive cloud bands reaching from tropical storms northeastward into the westerlies of middle latitudes. Fourteen well-defined cases of such cloud connections from western North Pacific tropical storms in the autumns of 1967, 1968 and 1969 are examined with respect to the large-scale circulation. The composited data show that the 300-mb westerlies over the North Pacific increase for several days following the onset of the cloud-band connections. Hemispheric kinetic energy for the whole troposphere tends to increase in similar fashion. These associations suggest that the injection of heat and moisture from tropical cyclones into the middle latitudes plays a significant role in the autumnal buildup of the planetary-scale circulation.
Abstract
The history of the Eastern Pacific tropical cyclone, Katherine, is presented for the period Scptcmhcr 8–17, 1963. It is shown that Katherine was the same storm as one which earlier had been named Jennifer.
The complementary nature of surface ship observations and satellite cloud photographs is well illustrated by this particular case. The experience suggests that both forms of data are essential to improved analyses and forecasts over data-sparse areas such as the tropical Eastern Pacific.
Abstract
The history of the Eastern Pacific tropical cyclone, Katherine, is presented for the period Scptcmhcr 8–17, 1963. It is shown that Katherine was the same storm as one which earlier had been named Jennifer.
The complementary nature of surface ship observations and satellite cloud photographs is well illustrated by this particular case. The experience suggests that both forms of data are essential to improved analyses and forecasts over data-sparse areas such as the tropical Eastern Pacific.
Abstract
No Abstract Available.
Abstract
No Abstract Available.
