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In honor of his teaching, research, and university administration, he received the Distinguished Professor award from the College of Arts and Science at Indiana State University. The Climate Specialty Group in the Association of American Geographers presented him the first Lifetime Achievement Award for his many contributions to the study of climatology and to that professional organization. We're sorry! We don't recognize your username or password. Please try again. The work is protected by local and international copyright laws and is provided solely for the use of instructors in teaching their courses and assessing student learning.

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Out of print. Climatology: An Atmospheric Science, 3rd Edition. John J. If You're an Educator Download instructor resources Additional order info. Description Taking the study of atmospheric science beyond the daily weather map, Climatology explores the broader impacts of weather and climate. The authors cover multiple facets of climate, many of which play a significant role in everyday life—and examine many topics, such as past climates that are seldom adequately covered in other introductory texts.

The science behind widely publicized events is explained within the systematic coverage of climate and climatology. In the Third Edition, data and information have been updated throughout and significant coverage is devoted to climate change. Weather is the condition of the atmosphere over a brief period of time. Climate represents the composite of day-to-day weather over a longer period of time.

Climate is the statistics of weather, usually over a year interval. It is measured by assessing the patterns of variation in temperature, humidity, atmospheric pressure, wind, precipitation, atmospheric particle count and other meteorological variables in a given region over long periods of time.

Climate differs from weather, in that weather only describes the short-term conditions of these variables in a given region. The earth-ocean-atmosphere system may be divided into a number of zones with each traditionally studied by a separate scientific discipline.

The atmosphere is the component of the system studied by climatologists and meteorologists. Historical climatology focuses primarily on climate changes throughout history and the effects of the climate on people and events over time.

The availability of recently released global ERA5 reanalysis with hourly resolution and horizontal spacing sufficient to sample local scale convective environments, allows construction of a global climatology and analysis of corresponding trends in the way that was not possible with prior reanalyses 35 , However, as each reanalysis features certain limitations related to model formulation, applied parameterizations and assimilation techniques, a validation using observed sounding profiles is necessary 37 , 38 , Thus, results based on reanalyses should be always interpreted with caution, especially concerning thermodynamic instability and modeled precipitation where systematic errors are present 39 , The climatological distribution of CAPE strongly reflects the availability of low-level moisture.

Enhanced CAPE is observed over tropical and subtropical zones, excluding the high-pressure areas over the oceans and subtropical deserts Fig.

However, despite these increases over water, land-based changes are more modest and observed only over northwestern India, the northern Great Plains of the United States, and the majority of Europe. As in Fig. Seasonally Supplementary Fig. These trends may represent the ongoing desertification in the former, and the weakness of the monsoon circulation in the latter Drying in the Northern Hemisphere subtropics and tropics have been also observed with decreasing trends in precipitation in 20th century by Zhang et al.

Although CAPE provides insight into whether the atmosphere has the potential to produce deep moist convection, convective initiation is necessary for the thunderstorm to occur. This problem is highlighted over locations such as southern Texas or the western Mediterranean Sea where high CAPE rarely results in convective development due to considerable inhibition 35 , Increases in CAPE, therefore, mean little for thunderstorms if the frequency of initiation does not increase as well 44 , For this reason, we also consider changes in ERA5 modeled convective precipitation CP that serve as a proxy for convective initiation.

The climatological distribution of CP Fig. Similar enhancement in CP is also observed within Kuroshiro, Agulhas, Brazilian and eastern Australian warm currents, and all cyclonically active regions in the mid-latitudes. Lower CP accumulations are observed within cold currents and regions of subtropical subsidence that inhibit convective development e. South Atlantic High. Few areas exhibit significant increases and these are mostly modest, predominantly over the Indian subcontinent, western China, parts of southern and northern Europe, Siberia and Arctic Ocean.

Over the latter two, these small increases are likely driven by increasing surface temperatures and moisture over the Northern Hemisphere high-latitude regions, promoting increasingly frequent shallow convective activity Seasonal trends follow the annual accumulation patterns, with the exception of southeastern Asia that experience increases during DJF, but decreases in SON Supplementary Fig. Trends in CP should be interpreted with caution especially over the tropics as reanalysis datasets are prone to systematic errors in this metric Our results only partially overlap with prior studies that suggested decreases in parts of tropical and subtropical areas over Northern Hemisphere 42 , 48 , with others indicating increases in the most extreme events or mixed trends 49 , Numbers within linear plots indicate trend per decade and p -value.

Thunderstorm severity is governed by storm organization, a process primarily driven by environmental vertical wind shear 13 , 14 , The climatological distribution of the 50 th percentile P50 of BS06 is well correlated with the baroclinically driven thermal wind, and, thus, the position of the jet streams.

The highest values in BS06 are observed across mid-latitudes where horizontal temperature gradients are the highest Figs. Conversely, the lowest BS06 occurs along the Equator where the horizontal temperature gradient is very small, and upper level air circulation is comparatively weak.

However, there are some regional exceptions like the Great Plains of the United States where high CAPE is also accompanied by strong BS06 and creates favorable conditions for severe thunderstorms producing strong tornadoes and very large hail.

Long-term trends in the P50 of BS06 are small both seasonally and annually in comparison to those for instability Fig. Wind shear has increased over the Southern Ocean, and the mid-latitudes southern South America, far southern Africa, the northern United States , where it has shifted slightly poleward.

Modest significant decreases have taken place in regions where jet streams are commonplace, including a corridor from eastern Brazil to Australia, southeastern Europe, northern Canada, and the Arctic Fig. Combining previously analyzed parameters CAPE, BS06, CP into environmental proxies for the occurrence of severe thunderstorms over the land surface similar to the approach of Brooks et al. Increases are minor and confined only to just a few hours per decade in summer over Europe, India, and western China Supplementary Fig.

Severe thunderstorm environments are more closely tied to the location of jet streams where strong vertical wind shear is available Fig. This shifts the peak frequency of severe thunderstorms away from the tropics towards mid-latitudes, predominantly downstream or eastward of significant topography. Regions such as the eastern half of the United States, La Plata Basin, southern Africa, southeastern China, Bangladesh, and southern Europe feature the most conducive environments for severe thunderstorms Fig.

Long-term trends of severe environments feature significant changes primarily across mid-latitudes Fig. Only grids over the land surface are taken into account at least 30 in any latitudinal band. Vertical solid lines indicate p -value below 0. However, when the additional ingredient of BS06 is considered for the severe thunderstorm proxy, there is a noticeable increase around the Equator.

These changes are larger in the Southern Hemisphere than in the Northern Hemisphere, reflecting the consistent decreases over South America, southern Africa, and eastern Australia. This suggests that although the overall number of favorable thunderstorm situations has been steadily decreasing across ITCZ, the fraction of environments supportive of severe weather relatively increased.

Validation of ERA5 with trends obtained from observed global sounding measurements provides greater context to the certainty of ERA5 results, and identifies which aspects should be interpreted with caution. However, it should be noted that rawinsonde observations are also not free of errors. This includes temporal inhomogeneities, limited spatial availability most of the stations are from mid-latitudes and limited sub-daily sampling and UTC , contrasting the hourly resolution of ERA5 39 , Trends in P50 BS06 derived from quality-controlled sounding measurements for stations with sufficient temporal record are generally in a good agreement with ERA5 Fig.

Robust decreases are observed over parts of Europe, Southeastern Asia, and Australia while modest and mostly insignificant changes occur over North America. Problematically, the availability of rawinsonde data from South America and Africa is too limited to derive reliable conclusions for trends across broader areas.

Trends for all rawinsonde observations combined together are presented on c. Only stations that passed a rigorous quality-control procedure with at least observations available for or UTC at least per year over 30 years are included in this analysis.

In sounding data, there are robust increases over Southeastern Asia and Australia, which is contrasted by the opposite pattern in ERA5 Fig. These results are broadly consistent with prior studies indicating that vertical wind shear is represented well in reanalyses, while thermodynamic indices like CAPE especially extremes such as P95 are less reliable 37 , 38 , Thus, it is difficult to validate whether trends in instability in ERA5 are realistic, especially over tropics and subtropics.

Combining all quality-controlled rawinsonde measurements suggest that over the last 4 decades P95 CAPE has been consistently increasing, while an opposite pattern was observed for P50 BS06 - both are statistically significant for both and UTC Fig. This result broadly confirms previous expectations based on climate simulations 57 , 58 , However, it is worth noting that the majority of stations evaluated in our study with good temporal coverage are from mid-latitudes, and thus evaluation of changes across the tropics is limited.

In this study, we evaluated global thunderstorm environments and their corresponding trends over the 41 year period — by using ERA5 reanalysis and rawinsonde observations. Although ERA5 is only a modeled approximation of real atmospheric conditions, it provides a continuous dataset in time and space with resolution allowing construction of climatologies in a way that was not possible with prior global reanalyses.

These changes are also accompanied by decreases in available energy represented by CAPE, and thus imply a lower frequency of environments favorable to thunderstorms with potential implications for water availability 60 , agricultural productivity, societal aspects, and desertification e.

Sahel region However, these results are in contrast to the current expectations of changes in response to a globally warming climate in CMIP5 projections, where an increase in heavy precipitation but also increased length of dry periods across tropics is anticipated 28 , 29 , 30 , Previous research has argued that robust weakening of the tropical circulation is seen across models, and that changes in the spatial pattern of precipitation are dominated by the shifts across convergence zones.

However, as concluded by Kent et al. Large uncertainties in simulating convection and cloud ice fundamental to lightning formation in global climate models were also noted by Finney et al.

Similar to our study, they found reductions in lightning days in Congo, but an increase in extreme lightning days. Mid-latitude changes to CAPE vary considerably in space, with modest decreases over the Southern Hemisphere and robust positive trends close to inland seas, over Europe, and the northern Great Plains of the United States.

Despite these increases, there are overall reductions in CP, and regional modulations in BS However, even with positive trends in BS06 over the La Plata Basin and Southern Africa, the frequency of severe thunderstorm environments decreased due to less frequent convective development according to ERA5.

This suggests that a prime consideration for assessing long-term changes to thunderstorm frequency needs to focus on convective initiation and its efficiency 35 , 45 , 62 rather than just the other ingredients, which is challenging to assess with observational data. Trends derived from rawinsonde observations for and UTC indicate significant increases in CAPE and reductions in BS06 across mid-latitudes, consistent with expectations of a changing climate 57 , 58 , However, by the same token, this also highlights that trends in the ERA5 reanalysis should be considered carefully, as they are not always consistent with observed records.

A likely driver of some of these changes is a globally increasing near-surface temperature and moisture that has accelerated since the s, especially considering high latitudes of the Northern Hemisphere Changes in the horizontal temperature gradients are also another important factor that influences strength and position of the mid-latitude jet streams 53 , 54 , 55 , that are a main driver of severe thunderstorms.

The disagreement between our results and CMIP5 projections of changes to convective environments by the end of the century may be a result of temporal inhomogeneities in the ERA5, an aspect of climate variability on the multi-decadal scale, or strong uncertainties in simulated future CP accumulations in GCMs Recent changes in atmospheric aerosols may be also a reason why historical trends in ERA5 differ from the projected climate change response.

As reanalysis records continue to lengthen, they will allow improved assessment of historical changes in convective environments, and provide greater context for projected scenarios in climate projections. Nevertheless, the ERA5 results presented here suggest that despite substantial increases in temperature since the s, fewer favorable thunderstorm environments are occurring over some regions, in contrast to the increases expected in a warmer future climate.

Other factors such as future expected decreases in vertical wind shear, relative humidity, and temperature lapse rates can also have a negative effect on the likelihood of convective storms and their severity, but large uncertainties in the models limit our confidence. After strict quality-control procedures explained in details in Taszarek et al. A final database consisted of 4,, profiles from stations for UTC, and 4,, profiles from stations for UTC Supplementary Fig. An increasing quality of rawinsonde measurements was observed with time as a higher fraction of profiles passed quality-control procedures over the recent years compared to s and s.

The underlying ERA5 convective parameterization that produces CP 67 applies a mass flux closure scheme with entrainment that triggers convection based on either surface fluxes or synoptic-scale motion, thereby providing greater confidence of initiation in a manner similar to the observed atmosphere.

In addition to individual variables, we also combine them into specific proxies to define conditions favorable to severe thunderstorms. Combining CAPE with vertical wind shear has been previously shown to distinguish well between non-severe, severe and significant severe thunderstorms across the United States 10 , 57 , Australia 9 , Europe 10 , South Africa 69 , and South America As these proxies have been originally developed for severe thunderstorms occurring over the land surface, in this study oceanic environments are not considered.

Another important aspect is that the majority of these proxies were designed based on mid-latitudes, thus their application in tropical and sub-tropical areas should be interpreted with caution. All variables were considered for the global domain at hourly resolution. To assess climatology and trends, we use 4 different metrics describing important elements of the environmental distribution: accumulation for CP , 50 th percentile for BS06 , 95 th percentile for CAPE and frequency of favorable severe thunderstorm environments.

These metrics are consistent with similar prior studies that evaluated convective trends on the regional scale 35 , 36 , We chose this metric due to its frequent application for evaluating robust trends in the atmospheric sciences where the underlying parameters exhibit interannual variability. Significance of the trend is assessed using a non-parametric Mann-Kendall two-tailed p -value at the 0.

Slope units are calculated for the annual change, but normalized to change per decade for simplicity of interpretation. Environmental proxies are an imperfect conditional approximation of convective activity, and should be interpreted with caution. As demonstrated by Tippett et al. This poses challenges, particularly when comparing different parts of the world with different underlying climatology.

Proxies used in this study were primarily developed for the mid-latitudes, and their performance over tropical and subtropical areas is uncertain. Thus, analyzing changes using these proxies will be burdened with some degree of inaccuracy, no matter the parameter chosen. Application of convective proxies obviously does not provide an explicit number of storm events, but it helps to define the approximate frequency to those that may most likely result in severe thunderstorms.

Additional limitations may be related to the model formulation of ERA5. For example, convective parameterizations may lead to errors in the vertical profile of temperature and moisture and subsequently influence metrics such as CAPE and modeled precipitation 25 , 37 , 38 , Although the defining concept of the reanalysis is to provide a consistent record of meteorological conditions over time, varying quality of assimilated data may be a source of specific biases that are smaller over the recent years 66 , Although it is beyond the scope of this paper to diagnose the source of such errors, it provides a caveat on the results and should be taken into consideration when interpreting results, especially over areas where differing trends are obtained for observations.

Nevertheless, ERA5 at least regionally compared to other global reanalyses is considered to be currently one of the best available tools for studying convective climatologies 35 , 36 , Munich Re. Thunderstorms, hail and tornadoes. Localised but extremely destructive.