scholarly journals The Interannual and Interdecadal Variability in Tropical Cyclone Activity: A Decade of Changes in the Climatological Character

2020 ◽  
Author(s):  
Anthony R. Lupo ◽  
Brendan Heaven ◽  
Jack Matzen ◽  
Jordan Rabinowitz
Keyword(s):  
Tropical Cyclones ◽  
Climate Models ◽  
North Indian Ocean ◽  
Interdecadal Variability ◽  
The West ◽  
Tropical Ocean ◽  
West Pacific ◽  
Previous Decade ◽  
Long Term Trends

During the last decade, there has been concern that the frequency or intensity of tropical cyclones (TCs) has increased. Also, climate models have shown varying results regarding the future occurrence and intensities of TC. Previous research from this group showed there is significant interannual and interdecadal variability in TC occurrence and intensity for some tropical ocean basins and sub-basins. This work examines global TC occurrence and intensity from 2010 to 2019 and compares this period to the same quantities from 1980 to 2009. The data used here are obtained from publicly available TC archives. Globally, the number of TC occurring over the latest decade is similar to the previous decade. However, while the 40-year trend shows an increase in TC, only intense hurricanes have shown an increase. The Atlantic Ocean and North Indian Ocean Basins show increases in TC activity, especially intense storms. The Southern Hemisphere and West Pacific Region show decreases in TC activity. In the West Pacific, intense TC did not increase, but the fraction of storms classified as intense increased. Only East Pacific TC activity showed no significant short- or long-term trends. Interannual and interdecadal variability in each sub-basin was found and there were some differences with previous work.

scholarly journals Long-term trends in the frequency of severe cyclones of Bay of Bengal : Observations and simulations

MAUSAM ◽  
2021 ◽  
Vol 58 (1) ◽  
pp. 59-66
Author(s):  
O. P. SINGH
Keyword(s):  
Tropical Cyclones ◽  
Bay Of Bengal ◽  
Climate Model ◽  
Model Simulation ◽  
Global Climate ◽  
Regional Climate ◽  
North Indian Ocean ◽  
Anthropogenic Activity ◽  
Long Term Trends

The east coast of India and the coasts of Bangladesh, Myanmar and Sri Lanka are vulnerable to the incidence of tropical cyclones of the Bay of Bengal. Every year these cyclones inflict heavy loss of life and property in this region. Global climate change resulting from anthropogenic activity is likely to manifest itself in the weather and climate of the Bay of Bengal region also. The long-term trends in the frequency and intensity of tropical cyclones of the Bay of Bengal during intense cyclonic months May, October and November is one such problem which has been addressed in the present paper.Utilizing the existing data of 129 years (1877-2005) pertaining to the tropical cyclone frequency and intensity in the Bay of Bengal during May, October and November, a study was undertaken to investigate the trends in the frequency of Severe Cyclonic Storms (SCS) during past decades. The results of the trend analysis reveal that the SCS frequency over the Bay of Bengal has registered significant increasing trends in past 129 years during the intense cyclonic months. It may be emphasized that these trends are long-term trends for more than hundred years based on statistical analyses which do not necessarily imply that SCS frequency has increased continuously decade after decade. As a matter of fact there has been a slight decrease in SCS frequency after peaking in the pentad 1966-1970, but this does not alter the long-term trend much. The intensification rate during November, which accounts for highest number of intense cyclones in the north Indian Ocean, has registered a steep rise of 26% per hundred years, implying that a tropical depression forming in the Bay of Bengal during November has a high probability to reach to severe cyclone stage. A regional climate model simulation revealed the enhanced cyclogenesis in the Bay of Bengal during May, October and November as a result of increased anthropogenic emissions in the atmosphere

Northeast Atlantic storminess in centennial reanalyses

2021 ◽  
Author(s):  
Oliver Krueger ◽  
Frauke Feser ◽  
Christopher Kadow ◽  
Ralf Weisse
Keyword(s):  
Climate Models ◽  
Numerical Models ◽  
Geostrophic Wind ◽  
Model Systems ◽  
Storm Activity ◽  
Northeast Atlantic ◽  
Wind Speeds ◽  
Long Term Trends ◽  
Storm Index

<p>Global atmospheric reanalyses are commonly applied for the validation of climate models, diagnostic studies, and driving higher resolution numerical models with the emphasis on assessing climate variability and long-term trends. Over recent years, longer reanalyses spanning a period of more than hundred years have become available. In this study, the variability and long-term trends of storm activity is assessed over the northeast Atlantic in modern centennial reanalysis datasets, namely ERA-20cm, ERA-20c, CERA-20c, and the 20CR-reanalysis suite with 20CRv3 being the most recent one. All reanalyses, except from ERA-20cm, assimilate surface pressure observations, whereby ERA-20C and CERA-20c additionally assimilate surface winds. For the assessment, the well-established storm index of higher annual percentiles of geostrophic wind speeds derived from pressure observations at sea level over a relatively densely monitored marine area is used.</p><p>The results indicate that the examined centennial reanalyses are not able to represent long-term trends of storm activity over the northeast Atlantic, particularly in the earlier years of the period examined when compared with the geostrophic wind index based on pressure observations. Moreover, the reanalyses show inconsistent long-term behaviour when compared with each other. Only in the latter half of the 20th century, the variability of reanalysed and observed storminess time series starts to agree with each other. Additionally, 20CRv3, the most recent centennial reanalysis examined, shows markedly improved results with increased uncertainty, albeit multidecadal storminess variability does not match observed values in earlier times before about 1920.</p><p>The behaviour shown by the centennial reanalyses are likely caused by the increasing number of assimilated observations, changes in the observational databases used, and the different underlying numerical model systems. Furthermore, the results derived from the ERA-20cm reanalysis that does not assimilate any pressure or wind observations suggests that the variability and uncertainty of storminess over the northeast Atlantic is high making it difficult to determine storm activity when numerical models are not bound by observations. The results of this study imply and reconfirm previous findings that the assessment of long-term storminess trends and variability in centennial reanalyses remains a rather delicate matter, at least for the northeast Atlantic region.</p>

scholarly journals Variability and past long-term changes of brominated very short-lived substances at the tropical tropopause

2020 ◽  
Vol 20 (11) ◽  
pp. 7103-7123
Author(s):  
Susann Tegtmeier ◽  
Elliot Atlas ◽  
Birgit Quack ◽  
Franziska Ziska ◽  
Kirstin Krüger
Keyword(s):  
Central America ◽  
Temporal Variability ◽  
Spatial And Temporal Variability ◽  
Positive Trend ◽  
The West ◽  
West Pacific ◽  
Mixing Ratios ◽  
Long Term Changes ◽  
Averaged Model

Abstract. Halogenated very short-lived substances (VSLSs), such as bromoform (CHBr3), can be transported to the stratosphere and contribute to the halogen loading and ozone depletion. Given their highly variable emission rates and their short atmospheric lifetimes, the exact amount as well as the spatio-temporal variability of their contribution to the stratospheric halogen loading are still uncertain. We combine observational data sets with Lagrangian atmospheric modelling in order to analyse the spatial and temporal variability of the CHBr3 injection into the stratosphere for the time period 1979–2013. Regional maxima with mixing ratios of up to 0.4–0.5 ppt at 17 km altitude are diagnosed to be over Central America (1) and over the Maritime Continent–west Pacific (2), both of which are confirmed by high-altitude aircraft campaigns. The CHBr3 maximum over Central America is caused by the co-occurrence of convectively driven short transport timescales and strong regional sources, which in conjunction drive the seasonality of CHBr3 injection. Model results at a daily resolution reveal isolated, exceptionally high CHBr3 values in this region which are confirmed by aircraft measurements during the ACCENT campaign and do not occur in spatially or temporally averaged model fields. CHBr3 injection over the west Pacific is centred south of the Equator due to strong oceanic sources underneath prescribed by the here-applied bottom-up emission inventory. The globally largest CHBr3 mixing ratios at the cold point level of up to 0.6 ppt are diagnosed to occur over the region of India, Bay of Bengal, and Arabian Sea (3); however, no data from aircraft campaigns are available to confirm this finding. Inter-annual variability of stratospheric CHBr3 injection of 10 %–20 % is to a large part driven by the variability of coupled ocean–atmosphere circulation systems. Long-term changes, on the other hand, correlate with the regional sea surface temperature trends resulting in positive trends of stratospheric CHBr3 injection over the west Pacific and Asian monsoon region and negative trends over the east Pacific. For the tropical mean, these opposite regional trends balance each other out, resulting in a relatively weak positive trend of 0.017±0.012 ppt Br per decade for 1979–2013, corresponding to 3 % Br per decade. The overall contribution of CHBr3 together with CH2Br2 to the stratospheric halogen loading accounts for 4.7 ppt Br, in good agreement with existing studies, with 50 % and 50 % being injected in the form of source and product gases, respectively.

scholarly journals Variability and long-term changes of brominated VSLS at the tropical tropopause

2019 ◽  
Author(s):  
Susann Tegtmeier ◽  
Elliot Atlas ◽  
Birgit Quack ◽  
Franziska Ziska ◽  
Kirstin Krüger
Keyword(s):  
Central America ◽  
Spatial And Temporal Variability ◽  
Positive Trend ◽  
The West ◽  
Asian Monsoon Region ◽  
West Pacific ◽  
Mixing Ratios ◽  
Long Term Changes ◽  
Averaged Model

Abstract. We combine available observational data sets with Lagrangian atmospheric modelling in order to analyze the spatial and temporal variability of the CHBr3 injection into the stratosphere. Regional maxima with mixing ratios of up to 0.4–0.5 ppt at 17 km altitude are diagnosed to be over Central America (1) and over the Maritime Continent/West Pacific (2), both of which are confirmed by high-altitude aircraft campaigns. The CHBr3 maximum over Central America is caused by the co-occurrence of convectively-driven short transport time scales and strong regional sources, which in conjunction drive the seasonality of CHBr3 injection. Model results at a daily resolution reveal isolated, exceptionally high CHBr3 values in this region which are confirmed by measurements during the ACCENT campaign and do not occur in spatially or temporally averaged model fields. CHBr3 injection over the West Pacific is centered south of the equator due to strong oceanic sources underneath prescribed by the here applied bottom-up emission inventory. The globally strongest stratospheric CHBr3 injection of up to 0.6 ppt is diagnosed to occur over the region of India, Bay of Bengal and Arabian Sea (3), however, no data from aircraft campaigns are available to confirm this finding. Interannual variability of stratospheric CHBr3 injection of 10–20 % is to a large part driven by the variability of coupled ocean-atmosphere circulation systems. Long-term changes, on the other hand, correlate with the regional SST trends resulting in positive trends of stratospheric CHBr3 injection over the West Pacific and Asian monsoon region and negative trends over the East Pacific. For the tropical mean, these opposite regional trends balance each other out resulting in a relatively weak positive trend of 0.017 ± 0.012 ppt Br/dec for 1979–2013, corresponding 3 % Br/dec. The overall contribution of CHBr3 together with CH2Br2 to the stratospheric halogen loading accounts for 4.7 ppt Br, in good agreement with existing studies, with 50 %/50 % being injected in form of source and product gases, respectively.

scholarly journals Long-term trends of hail-related weather types in an ensemble of regional climate models using a Bayesian approach

2012 ◽  
Vol 117 (D15) ◽  
pp. n/a-n/a ◽  
Author(s):  
M.-L. Kapsch ◽  
M. Kunz ◽  
R. Vitolo ◽  
T. Economou
Keyword(s):  
Bayesian Approach ◽  
Climate Models ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Weather Types ◽  
Long Term Trends

scholarly journals Long-Term Trends in Downwelling Spectral Infrared Radiance over the U.S. Southern Great Plains

2011 ◽  
Vol 24 (18) ◽  
pp. 4831-4843 ◽  
Author(s):  
P. Jonathan Gero ◽  
David D. Turner
Keyword(s):  
Great Plains ◽  
Climate Models ◽  
Southern Great Plains ◽  
Infrared Radiance ◽  
Term Change ◽  
Atmospheric Radiation Measurement ◽  
Long Term Trends ◽  
Thin Cloud ◽  
The U.S

Abstract A trend analysis was applied to a 14-yr time series of downwelling spectral infrared radiance observations from the Atmospheric Emitted Radiance Interferometer (AERI) located at the Atmospheric Radiation Measurement Program (ARM) site in the U.S. Southern Great Plains. The highly accurate calibration of the AERI instrument, performed every 10 min, ensures that any statistically significant trend in the observed data over this time can be attributed to changes in the atmospheric properties and composition, and not to changes in the sensitivity or responsivity of the instrument. The measured infrared spectra, numbering more than 800 000, were classified as clear-sky, thin cloud, and thick cloud scenes using a neural network method. The AERI data record demonstrates that the downwelling infrared radiance is decreasing over this 14-yr period in the winter, summer, and autumn seasons but it is increasing in the spring; these trends are statistically significant and are primarily due to long-term change in the cloudiness above the site. The AERI data also show many statistically significant trends on annual, seasonal, and diurnal time scales, with different trend signatures identified in the separate scene classifications. Given the decadal time span of the dataset, effects from natural variability should be considered in drawing broader conclusions. Nevertheless, this dataset has high value owing to the ability to infer possible mechanisms for any trends from the observations themselves and to test the performance of climate models.

scholarly journals Trends and fluctuations of the cyclonic systems over North Indian Ocean

MAUSAM ◽  
2021 ◽  
Vol 52 (1) ◽  
pp. 37-46
Author(s):  
D. V. BHASKAR RAO ◽  
C. V. NAIDU ◽  
B. R. SRINIVASA RAO
Keyword(s):  
Time Series ◽  
Indian Ocean ◽  
Maximum Entropy Method ◽  
Entropy Method ◽  
North Indian Ocean ◽  
Pass Filter ◽  
Long Term Trends ◽  
High Pass ◽  
Cyclone Frequency

The data of the monthly cyclone frequencies over North Indian Ocean for the period 1877-1998 has been analysed to study the long-term trends and fluctuations. Analysis has been made separately for depressions and cyclones for the pre-monsoon, monsoon and post-monsoon seasons along with the annual frequencies. The data was subjected to 11-year moving averages and the epochs of increasing and decreasing trends have been identified. A consistent decreasing trend after 1950s is a notable feature.   The time series of the monthly cyclone frequency were passed through a high-pass filter to eliminate periods greater than 21 years and then subjected to spectrum analysis using Maximum Entropy Method to obtain dominant periodicities. Three significant periodicities at 2.2-2.8; 3.5-6.5 and 10-15 years have been identified which could be attributed to QBO, ENSO and decadal frequencies.

Long-term trends in loblolly pine productivity and stand characteristics in response to thinning and fertilization in the West Gulf region

2004 ◽  
Vol 192 (1) ◽  
pp. 71-96 ◽  
Author(s):  
M.A. Sword Sayer ◽  
J.C.G. Goelz ◽  
J.L. Chambers ◽  
Z. Tang ◽  
T.J. Dean ◽  
...  
Keyword(s):  
Loblolly Pine ◽  
Gulf Region ◽  
The West ◽  
Long Term Trends ◽  
Stand Characteristics

Long-term Trend Comparison of Planetary Boundary Layer Height in Observations and CMIP6 models over China

2021 ◽  
Author(s):  
Man Yue ◽  
Minghuai Wang ◽  
Jianping Guo ◽  
Haipeng Zhang ◽  
Xinyi Dong ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Cloud Cover ◽  
Climate Models ◽  
Term Trend ◽  
Cloud Radiative Effect ◽  
Low Cloud ◽  
Long Term Trends ◽  
Low Cloud Cover ◽  
Long Term Trend

<p>The planetary boundary layer (PBL) plays an essential role in climate and air quality simulations. Large uncertainties remain in understanding the long-term trend of PBL height (PBLH) and its simulation. Here we use the radiosonde data and reanalysis datasets to analyze PBLH long-term trends over China, and to further evaluate the performance of CMIP6 climate models in simulating these trends. Results show that the observed long-term “positive to negative” trend shift of PBLH is related to the variation in the surface upward sensible heat flux (SHFLX) which is further controlled by the synergistic effect of low cloud cover (LCC) and soil moisture (SM) changes. Variabilities in low cloud cover and soil moisture directly influence the energy balance via surface net downward shortwave flux (SWF) and the latent heat flux (LHFLX), respectively. We have found that the CMIP6 climate models cannot reproduce the observed PBLH long-term trend shift over China. The CMIP6 results show an overwhelming continuous downward PBLH trend during the 1979-2014 period, which is caused by the poorly simulated long-term changes of cloud radiative effect. Our results reveal that the long-term cloud radiative effect simulation is critical for CMIP6 models in reproducing the PBLH long-term trends. This study highlights the importance of low cloud cover and soil moisture processes in modulating PBLH long-term variations and calls attentions to improve these processes in climate models in order to improve the PLBH long-term trend simulations.</p>

scholarly journals Landfalling Tropical Cyclones along the Eastern Pacific Coast between the Sixteenth and Twentieth Centuries

2013 ◽  
Vol 26 (12) ◽  
pp. 4219-4230 ◽  
Author(s):  
Marni Pazos ◽  
Blanca Mendoza
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Pacific Coast ◽  
Eastern Pacific ◽  
Historical Time ◽  
Eastern Pacific Ocean ◽  
Mexican Pacific ◽  
Long Term Trends ◽  
Landfalling Tropical Cyclones

Abstract Numerous studies have been conducted to document long-term trends in tropical cyclone (TC) activity. However, the eastern Pacific has not received as much attention as other basins. Here the authors attempt the identification of TC formation in the Mexican eastern Pacific Ocean before 1950. Using bibliographical and historical file consultation, they constructed a catalog of events related to intense storms and possible TCs that made landfall on the Mexican Pacific coasts. Between 1536 and 1948 they found a total of 119 events related to TCs. Then, using the Saffir–Simpson scale and the climatology of the region as the criteria to evaluate each event, they found 85 TCs. Furthermore, they constructed a historical time series of TCs between 1701 and 2010. The spectral analysis showed periodicities of ~2.6, 4, 5, 12, 16, 39, and 105 years that coincide with some large-scale climatic phenomena and also with solar activity. In particular, the ~12-yr cycle is the most persistent periodicity in this study.

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