The Unexpected Relationship Between Extreme Shear Events and AMO

The vertical shear–the change in wind speed with height-of horizontal winds is a serious threat to the safety of aircraft. Yet their global distribution is not fully understood. We creatively used a precise method to calculate different types of vertical shear at four isobaric surfaces during the period of 1979~2018. The occurrence of severe shear events has increased by 19%, and they mostly occur over the equatorial ocean and within the mid-high latitude zone of the Northern hemisphere, while light shear event occurrence has been reduced by 21%. Variations of severe shear are modulated by the Atlantic Multidecadal Oscillation (AMO), which affects the frequency of shear events by influencing the intertropical convergence zone (ITCZ). Our study implies that severe shear events are regulated by internal climate variability.

A STATISTICAL MODEL OF WINTER/SPRING POLAR OZONE

Satellite measurements provided by NASA (USA) at http://ozonewatch.gsfc.nasa.gov are used to study the variability and interdependence of polar ozone, polar temperature, and mean zonal wind. A model of winter/spring polar ozone in the Arctic and Antarctic is constructed using data on polar temperatures at 30, 70, and 100 hPa levels and mean zonal wind at 10 and 70 hPa levels in the latitude zone of 45°-75°. The results of the statistical analysis of the 1979-2020 polar ozone calculation errors are presented.

Bi-Temporal Analysis of Spatial Changes of Boreal Forest Cover and Species in Siberia for the Years 1985 and 2015

Boreal forest is a sensitive indicator of the influence of climate change. It can quantify the level and spatial divergence of forest change for forest resources and carbon cycle research. This study selected a typical boreal forest affected by few human activities as a research area, in Siberia, with a latitude span of 51°N–69°N. A total of 150 Landsat images of this area acquired in 1985 and 2015 were collected. A hierarchical classification approach was first established to retrieve the information of forest cover and species. The forested and nonforested lands were discriminated by the decision tree method and, furthermore, the forested land was classified to broad-leaved and coniferous forests by a random forest algorithm. The overall accuracy was 90.37%, which indicates the validity of the approach. Finally, the quantitative information of the forest cover and species changes in each latitude zone of every 2° was analyzed. The results show that the overall boreal forest cover increased by 5.11% over the past three decades, with broad-leaved forest increasing by 3.54% and coniferous forest increasing by 1.57%. In addition, boreal forest increased in every latitude zone, and the spatial divergence of the changes of the boreal forest cover and species in different latitude zones were significant. Finally, broad-leaved forest increased more rapidly than coniferous forest, and the greatest increase, of up to 5.77%, occurred in the zone of 55°N–57°N.

The Global Distribution of Cirrus Clouds Reflectance Based on MODIS Level-3 Data

Cirrus clouds are crucially important to weather, climate and earth energy balance studies. The distribution of cirrus reflectance with latitude and season is an interesting topic in atmospheric sciences. The monthly mean Level-3 MODIS cirrus reflectance is used to analyze the global distribution of cirrus clouds, which covers a period from 1 March 2000 to 28 February 2018. The latitude, from 90° S to 90° N, is divided into 36 latitude zones with 5° interval. Data in each latitude zone are analyzed. The research results show that the slopes of cirrus reflectance variation in the Northern and Southern Hemisphere are −1.253 × 10−4/year and –1.297 × 10−4/year, respectively. The yearly-average cirrus reflectance reveals strong negative correlation with time in the Northern Hemisphere, i.e., the correlation coefficient is −0.761. Then the statistical analysis of cirrus reflectance is performed in different seasons, the results show that cirrus reflectance varies obviously with seasonal change. Additionally, for the [30°, 90°] latitude regions, cirrus reflectance reaches the minimum in summer and the maximum in winter in the Southern and Northern Hemisphere.

Trend quality ozone from NPP OMPS: the version 2 processing

A version 2 processing of data from two ozone monitoring instruments on Suomi NPP, the OMPS nadir ozone mapper and the OMPS nadir ozone profiler, has now been completed. The previously released data were useful for many purposes but were not suitable for use in ozone trend analysis. In this processing, instrument artifacts have been identified and corrected, an improved scattered light correction and wavelength registration have been applied, and soft calibration techniques were implemented to produce a calibration consistent with data from the series of SBUV/2 instruments. The result is a high-quality ozone time series suitable for trend analysis. Total column ozone data from the OMPS nadir mapper now agree with data from the SBUV/2 instrument on NOAA 19 with a zonal average bias of −0.2 % over the 60∘ S to 60∘ N latitude zone. Differences are somewhat larger between OMPS nadir profiler and N19 total column ozone, with an average difference of −1.1 % over the 60∘ S to 60∘ N latitude zone and a residual seasonal variation of about 2 % at latitudes higher than about 50∘. For the profile retrieval, zonal average ozone in the upper stratosphere (between 2.5 and 4 hPa) agrees with that from NOAA 19 within ±3 % and an average bias of −1.1 %. In the lower stratosphere (between 25 and 40 hPa) agreement is within ±3 % with an average bias of +1.1 %. Tropospheric ozone produced by subtracting stratospheric ozone measured by the OMPS limb profiler from total column ozone measured by the nadir mapper is consistent with tropospheric ozone produced by subtracting stratospheric ozone from MLS from total ozone from the OMI instrument on Aura. The agreement of tropospheric ozone is within 10 % in most locations.

Trend Quality Ozone from NPP OMPS: the Version 2 Processing

A version 2 processing of data from two ozone monitoring instruments on Suomi NPP, the OMPS nadir ozone mapper and the OMPS nadir ozone profiler, has now been completed. The previously released data were useful for many purposes but were not suitable for use in ozone trend analysis. In this processing, instrument artifacts have been identified and corrected, an improved scattered light correction and wavelength registration have been applied, and soft calibration techniques were implemented to produce a calibration consistent with data from the series of SBUV/2 instruments. The result is a high quality ozone time series suitable for trend analysis. Total column ozone data from the OMPS nadir mapper now agree with data from the SBUV/2 instrument on NOAA 19 with a zonal average bias of −0.2 % over the 60° S to 60° N latitude zone. Differences are somewhat larger between OMPS nadir profiler and N19 total column ozone, with an average difference of −1.1 % over the 60° S to 60° N latitude zone and a residual seasonal variation of about 2 % at latitudes higher than about 50 degrees. For the profile retrieval, zonal average ozone in the upper stratosphere (between 2.5 and 4 hPa) agrees with that from NOAA 19 within ±3 % and an average bias of −1.1 %. In the lower stratosphere (between 25 and 40 hPa) agreement is within ±3 % with an average bias of +1.1 %. Tropospheric ozone produced by subtracting stratospheric ozone measured by the OMPS limb profiler from total column ozone measured by the nadir mapper is consistent with tropospheric ozone produced by subtracting stratospheric ozone from MLS from total ozone from the OMI instrument on Aura. The agreement of tropospheric ozone is within 10 % in most locations.

Optimum Tilt Angle Determine

After treating extraterrestrial and terrestrial solar radiations in the previous chapters, the use of this information in treating an important question regarding the installation of fixed solar systems, namely the tilt and orientation of the solar receivers, becomes possible. There are several rules that guide designers in this field. These rules are called the rules of thumb. There are two rules that are directly related to the subject of this chapter. One of these two rules says that a solar collector should be orientated towards Equator. The other one says that solar collector should have a latitude tilt value. Are these two rules valid all over the world? The present chapter focuses on presenting an algorithm for determining the optimum tilt angle all over the world and for any collector azimuth angle. The Earth surface, located between latitudes 66.45oS and 66.45oN, is divided into 3 characteristic zones. The first zone is the tropical between latitudes 23.45oS and 23.45oN. The second zone is the mid-latitude zone between 23.45oN and 43.45oN and between 23.45oS and 43.45oS. The third zone is the high-latitude zone between 43.45oN and 66.45oN and between 43.45oS and 66.45oS. For each of these zones an adequate method is proposed for calculating the solar collector optimum tilt. Moreover, four simple equations are proposed for predicting daily optimum tilt angle and optimum tilt angle for any number of consecutive days. It is found that the above mentioned rules of thumb are not applicable in the tropical zone while they could be applied with a sufficient accuracy when dealing with fixed installations all over the year in the mid- and high latitude zones.