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- Author or Editor: R. M. Nagatani x
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Abstract
Significant advances have been made recently both in observational studies and in dynamical numerical simulations of stratosphere warmings. Observed characteristics of warmings are reviewed, with discussion of the trajectory of warm cells, the vertical and horizontal scale of the warm-air systems, the time-scale of warming, circulation effects, initial zonal flow conditions before a warming, and details of the energy budget before and after warming. Distinctions are drawn between the 1973 and 1963 types of warmings, which involved a poleward advance of warm air in wave 1 and wave 2, respectively. In contrast to the warming of 1963, a strong baroclinic conversion of eddy potential to eddy kinetic energy was not discerned in 1973, but both events were preceded by extraordinarily large fluxes from the troposphere. The results of dynamical warming simulations by several investigators reflect varying degrees of success in reproducing observed features of warmings. The results of Matsuno and Newson closely resemble important features of the 1963 and 1973 warmings, respectively. Some areas of apparent disagreement are explainable in part by the difficulty of matching the phase of simulated and observed events in time and space. Factors requiring elucidation include the physical process accounting for upward energy fluxes leading to warmings, the role of wave interaction in the stratosphere, and the associated tropospheric synoptic conditions.
Abstract
Significant advances have been made recently both in observational studies and in dynamical numerical simulations of stratosphere warmings. Observed characteristics of warmings are reviewed, with discussion of the trajectory of warm cells, the vertical and horizontal scale of the warm-air systems, the time-scale of warming, circulation effects, initial zonal flow conditions before a warming, and details of the energy budget before and after warming. Distinctions are drawn between the 1973 and 1963 types of warmings, which involved a poleward advance of warm air in wave 1 and wave 2, respectively. In contrast to the warming of 1963, a strong baroclinic conversion of eddy potential to eddy kinetic energy was not discerned in 1973, but both events were preceded by extraordinarily large fluxes from the troposphere. The results of dynamical warming simulations by several investigators reflect varying degrees of success in reproducing observed features of warmings. The results of Matsuno and Newson closely resemble important features of the 1963 and 1973 warmings, respectively. Some areas of apparent disagreement are explainable in part by the difficulty of matching the phase of simulated and observed events in time and space. Factors requiring elucidation include the physical process accounting for upward energy fluxes leading to warmings, the role of wave interaction in the stratosphere, and the associated tropospheric synoptic conditions.
Abstract
The most long-lived satellite set of ozone observations, to date, is that derived from the Backscatter Ultraviolet (BUV) ozone sensor on Nimbus 4 and extends from April 1970 through 1976. Unfortunately, this experiment suffered spacecraft power limitations which limited the spatial and temporal coverage and also appears to have suffered from long-term drifts which may be associated with changes in the instrument characteristics or the incident solar flux. We have developed techniques to account for these problems and our purpose here is to present results of the BUV total ozone variations and compare them with those from ground-based observations, specifically the computations of Angell and Korshover (1978).
After adjustments for the spatial gaps and comparison with concurrent Dobson ground-based observations, no significant trend was found in the BUV data over the years 1970-74. This finding is in contrast to a general decrease of ∼2% during the same period appearing in the data of Angell and Korshover. The difference in these results is discussed in terms of the geographic sampling and the methods of hemispheric integration.
Abstract
The most long-lived satellite set of ozone observations, to date, is that derived from the Backscatter Ultraviolet (BUV) ozone sensor on Nimbus 4 and extends from April 1970 through 1976. Unfortunately, this experiment suffered spacecraft power limitations which limited the spatial and temporal coverage and also appears to have suffered from long-term drifts which may be associated with changes in the instrument characteristics or the incident solar flux. We have developed techniques to account for these problems and our purpose here is to present results of the BUV total ozone variations and compare them with those from ground-based observations, specifically the computations of Angell and Korshover (1978).
After adjustments for the spatial gaps and comparison with concurrent Dobson ground-based observations, no significant trend was found in the BUV data over the years 1970-74. This finding is in contrast to a general decrease of ∼2% during the same period appearing in the data of Angell and Korshover. The difference in these results is discussed in terms of the geographic sampling and the methods of hemispheric integration.
Abstract
A major question concerning the observed long-term changes of zonal average tow ozone has always been that the spatially limited ground-based ozone sampling sites are susceptible to a sampling problem. That is, the regional (or station) averages are influenced by shifts of the ozone wave patterns with respect to the sites such that a trend may be indicated that is not necessarily indicative of the actual zonal average. In order to help determine whether these sampling errors are short-term random features or have long-term components, we have utilized available synoptic analyses of the 100 mb height patterns (1964–16) and the observation that the 100 mb heights and tow 03 patterns in the midlatitudes of the Northern Hemisphere are negatively correlated. Accordingly, the ridge-trough patterns in the 100 mb height field at 50°N from 1964–76 are sampled over the domain of the ground-based 03 observing sites and a zonal average of 100 mb heights calculated using, the area-weighting functions of Angell and Korshover. These zonal averages are compared with the actual zonal average computed from all data and the results noted as a function of time. Utilizing linear 100 mb height– total 03 regression relationships, the zonal average total ozone sampling error is on the order of ±2% for midlatitudes of the Northern Hemisphere with a long-term component. With this result, the general shape of the midlatitude O3 trends determined from the ground-based observations appears to be real and not an artifact of the spatially limited ground-based sample. In fact, the increase of ozone from the mid-1960' to early 1970's may be even greater than previously suggested.
Abstract
A major question concerning the observed long-term changes of zonal average tow ozone has always been that the spatially limited ground-based ozone sampling sites are susceptible to a sampling problem. That is, the regional (or station) averages are influenced by shifts of the ozone wave patterns with respect to the sites such that a trend may be indicated that is not necessarily indicative of the actual zonal average. In order to help determine whether these sampling errors are short-term random features or have long-term components, we have utilized available synoptic analyses of the 100 mb height patterns (1964–16) and the observation that the 100 mb heights and tow 03 patterns in the midlatitudes of the Northern Hemisphere are negatively correlated. Accordingly, the ridge-trough patterns in the 100 mb height field at 50°N from 1964–76 are sampled over the domain of the ground-based 03 observing sites and a zonal average of 100 mb heights calculated using, the area-weighting functions of Angell and Korshover. These zonal averages are compared with the actual zonal average computed from all data and the results noted as a function of time. Utilizing linear 100 mb height– total 03 regression relationships, the zonal average total ozone sampling error is on the order of ±2% for midlatitudes of the Northern Hemisphere with a long-term component. With this result, the general shape of the midlatitude O3 trends determined from the ground-based observations appears to be real and not an artifact of the spatially limited ground-based sample. In fact, the increase of ozone from the mid-1960' to early 1970's may be even greater than previously suggested.
Abstract
Ozone estimates from observations by the NOAA-16 Solar Backscattered Ultraviolet (SBUV/2) instrument and Television Infrared Observation Satellite (TIROS-N) Operational Vertical Sounder (TOVS) are used to describe the vertical structure of ozone in the anomalous 2002 polar vortex. The SBUV/2 total ozone maps show that the ozone hole was pushed off the Pole and split into two halves due to a split in the midstratospheric polar vortex in late September. The vortex split and the associated transport of high ozone from midlatitudes to the polar region reduced the ozone hole area from 18 × 106 km2 on 20 September to 3 × 106 km2 on 27 September 2002. A 23-yr time series of SBUV/2 daily zonal mean total ozone amounts between 70° and 80°S shows record high values [385 Dobson units (DU)] during the late-September 2002 warming event. The transport and descent of high ozone from low latitudes to high latitudes between 60 and 15 mb contributed to the unusual increase in total column ozone and a small ozone hole estimated using the standard criterion (area with total ozone < 220 DU). In contrast, TOVS observations show an ozone-depleted region between 0 and 24 km, indicating that ozone destruction was present in the elongated but unsplit vortex in the lower stratosphere. During the warming event, the low-ozone regions in the middle and upper stratosphere were not vertically aligned with the low-ozone regions in the upper troposphere and lower stratosphere. This offset in the vertical distribution of ozone resulted in higher total column ozone masking the ozone depletion in the lower stratosphere and resulting in a smaller ozone hole size estimate from satellite total ozone data.
Abstract
Ozone estimates from observations by the NOAA-16 Solar Backscattered Ultraviolet (SBUV/2) instrument and Television Infrared Observation Satellite (TIROS-N) Operational Vertical Sounder (TOVS) are used to describe the vertical structure of ozone in the anomalous 2002 polar vortex. The SBUV/2 total ozone maps show that the ozone hole was pushed off the Pole and split into two halves due to a split in the midstratospheric polar vortex in late September. The vortex split and the associated transport of high ozone from midlatitudes to the polar region reduced the ozone hole area from 18 × 106 km2 on 20 September to 3 × 106 km2 on 27 September 2002. A 23-yr time series of SBUV/2 daily zonal mean total ozone amounts between 70° and 80°S shows record high values [385 Dobson units (DU)] during the late-September 2002 warming event. The transport and descent of high ozone from low latitudes to high latitudes between 60 and 15 mb contributed to the unusual increase in total column ozone and a small ozone hole estimated using the standard criterion (area with total ozone < 220 DU). In contrast, TOVS observations show an ozone-depleted region between 0 and 24 km, indicating that ozone destruction was present in the elongated but unsplit vortex in the lower stratosphere. During the warming event, the low-ozone regions in the middle and upper stratosphere were not vertically aligned with the low-ozone regions in the upper troposphere and lower stratosphere. This offset in the vertical distribution of ozone resulted in higher total column ozone masking the ozone depletion in the lower stratosphere and resulting in a smaller ozone hole size estimate from satellite total ozone data.
