pinecone/core-2020-05-10-deduplication huggingface dataset:
Cold surge episodes over southeastern Brazil - a potential vorticity perspective

Most intense cold surges and associated frost events in southern and southeastern Brazil are characterized by a large amplitude trough over South America extending toward tropical latitudes and a ridge to the west of it over the Pacific Ocean. In this study, potential vorticity (PV) streamers serve to examine the flow condition leading to cold surges. Case studies suggest that several PV anomalies are related to cold surge episodes: (1) the potential vorticity unit (2-PVU) isoline upstream of South America becomes progressively more distorted prior and during the cold surge episode, indicating a flow situation which is conducive for Rossby wave breaking and hence a flow which strongly deviates from zonality; (2) the initial stage of a cold surge episode is characterized by a northward bulging of high-PV air to the east of the Andes, resulting in a PV streamer whose northern end reaches Uruguay and southeastern Brazil; the strong PV gradient on its western flank constitutes a flow configuration that induces and maintains the transport of sub-Antarctic air toward the subtropics; (3) a distinct negative PV anomaly, a blocking, originates over the eastern South Pacific, upstream of the South America sector. A composite analysis of 27 cold surges is performed for stratospheric PV streamer frequency on several isentropic surfaces. It reveals that equatorward wave breaking over South America and the western South Atlantic represents an important potential component of the dynamics of intense cold surges. The indications are most pronounced around the isentropic levels of 320 K and immediately before the day with largest temperature drops over subtropical Brazil
Tropopause level Rossby wave breaking in the Northern Hemisphere: a feature-based validation of the ECHAM5-HAM climate model

Breaking synoptic-scale Rossby waves (RWB) at the tropopause level are central to the daily weather evolution in the extratropics and the subtropics. RWB leads to pronounced meridional transport of heat, moisture, momentum, and chemical constituents. RWB events are manifest as elongated and narrow structures in the tropopause-level potential vorticity (PV) field. A feature-based validation approach is used to assess the representation of Northern Hemisphere RWB in present-day climate simulations carried out with the ECHAM5-HAM climate model at three different resolutions (T42L19, T63L31, and T106L31) against the ERA-40 reanalysis data set. An objective identification algorithm extracts RWB events from the isentropic PV field and allows quantifying the frequency of occurrence of RWB. The biases in the frequency of RWB are then compared to biases in the time mean tropopause-level jet wind speeds. The ECHAM5-HAM model captures the location of the RWB frequency maxima in the Northern Hemisphere at all three resolutions. However, at coarse resolution (T42L19) the overall frequency of RWB, i.e. the frequency averaged over all seasons and the entire hemisphere, is underestimated by 28%.The higher-resolution simulations capture the overall frequency of RWB much better, with a minor difference between T63L31 and T106L31 (frequency errors of −3.5 and 6%, respectively). The number of large-size RWB events is significantly underestimated by the T42L19 experiment and well represented in the T106L31 simulation. On the local scale, however, significant differences to ERA-40 are found in the higher-resolution simulations. These differences are regionally confined and vary with the season. The most striking difference between T106L31 and ERA-40 is that ECHAM5-HAM overestimates the frequency of RWB in the subtropical Atlantic in all seasons except for spring. This bias maximum is accompanied by an equatorward extension of the subtropical westerlies
Changes in terrestrial water storage versus rainfall and discharges in the Amazon basin

International audienceThis study examines how the interannual variability of rainfall impacts the land water storage in the Amazon basin during the 2003-2010 time span at monthly time-scale using respectively, Tropical Rainfall Measuring Mission (TRMM) and Gravity Recovery And Climate Experiment (GRACE) satellite observations. Monthly estimates of GRACE-based terrestrial water storage (TWS) are compared to (1) TRMM rainfall, (2) in situ discharges at the outlet of the major sub-basins of the Amazon over 2003-2010 to characterize the redistribution of precipitation on land water. The time-variations of land water storage derived from GRACE are consistent with those of rainfall and discharges at basin and sub-basin scales even at interannual time-scales (correlation generally greater than 0.7). The study of the relationship between these two quantities reveals large differences in terms of rainfall amount, water storage, time delays, resulting of the water transport among the sub-basins of the Amazon. The analysis of GRACE data has enabled identification of the signature of the recent extreme climatic events (droughts of 2005 and 2010, flood of 2009) on the land water storage, in terms of spatial patterns and intensity. These results are in good agreement with what was observed on independent datasets (water levels and discharges, vegetation activity, forest fires, and drought index), highlighting the interest of gravimetry from space missions for the characterization of the interannual variability of the TWS. GRACE data offer the unique opportunity to monitor the hydrological cycle in ungauged basins where reliable observations of rainfall and discharges are missing
Snow variability in the Swiss Alps 1864-2009

We present a climate analysis of nine unique Swiss Alpine new snow series that have been newly digitized. The stations cover different altitudes (450–1860 m asl) and all time series cover more than 100 years (one from 1864 to 2009). In addition, data from 71 stations for the last 50–80 years for new snow and snow depth are analysed to get a more complete picture of the Swiss Alpine snow variability. Important snow climate indicators such as new snow sums (NSS), maximum new snow (MAXNS) and days with snowfall (DWSF) are calculated and variability and trends analysed. Series of days with snow pack (DWSP) ≥ 1 cm are reconstructed with useful quality for six stations using the daily new snow, local temperature and precipitation data. Our results reveal large decadal variability with phases of low and high values for NSS, DWSF and DWSP. For most stations NSS, DWSF and DWSP show the lowest values recorded and unprecedented negative trends in the late 1980s and 1990s. For MAXNS, however, no clear trends and smaller decadal variability are found but very large MAXNS values (>60 cm) are missing since the year 2000. The fraction of NSS and DWSP in different seasons (autumn, winter and spring) has changed only slightly over the ∼150 year record. Some decreases most likely attributable to temperature changes in the last 50 years are found for spring, especially for NSS at low stations. Both the NSS and DWSP snow indicators show a trend reversal in most recent years (since 2000), especially at low and medium altitudes. This is consistent with the recent ‘plateauing’ (i.e. slight relative decrease) of mean winter temperature in Switzerland and illustrates how important decadal variability is in understanding the trends in key snow indicators
Simulating the surface energy balance over two contrasting urban environments using the Community Land Model Urban

A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contrasting urban environments of Toulouse (France) and Melbourne (Australia). For the latter, three measurement sites are available characterized by a varying amount of vegetation, which supports a detailed assessment of the representation of urban vegetation in CLMU. For Toulouse, observed roof, wall and road surface temperatures allow for a detailed evaluation of the anthropogenic heat parameterization. Overall, CLMU performs well in simulating the canyon and urban surface temperatures, anthropogenic heat flux and urban energy balance, with an overall better performance for the dense old city centre of Toulouse in comparison to the more vegetated sites in Melbourne. Results for the latter sites reveal that the pervious road fraction provides a reasonable approximation of vegetation in the urban canyon while the tile approach often results in an underestimation of latent heat fluxes. A detailed analysis of the radiative, turbulent and anthropogenic heat fluxes as well as surface temperatures for Toulouse point to a complex interaction between urban surfaces and canyon properties. Decoupling the roof from the urban canyon to the atmosphere aloft is shown to be important. Our findings suggest that more evaluation is necessary for contrasting urban geometries in order to obtain a better understanding of the interaction between the roof surface on the one hand and canyon air and air aloft on the other hand. The results simultaneously reveal a trade-off in errors between surface temperatures, radiative and turbulent fluxes and anthropogenic heat which again stresses the importance of the intended model application. Also, our results suggest that model complexity should, perhaps, relate to the site complexity. These results provide a robust basis for the construction of additional sensitivity experiments, tailored towards the intended application for urban climate mitigation studies.status: publishe
Variability properties of daily and monthly observed near-surface temperatures in Uganda : 1960-2008

Variability and trends in daily and monthly near-surface temperatures in Uganda, collected over the period
1960–2008 (49 years), are analysed. For this purpose, daily observational maximum and minimum temperature records
from eight selected stations in Uganda were acquired from the Uganda Meteorological Department (UMD). Data collected
by the UMD are quality controlled through a rigorous process before being archived. The data received were tested for
homogeneity, gaps were filled and correlation analyses were used for validation of area average series. Statistical techniques
(e.g. Mann–Kendall and Linear Regression) were employed to analyse temperature variability and to obtain temperature
trends. Findings indicate that intra-annual temperature shows reduced variability over recent decades, but which is not
statistically significant. Results also demonstrated that maximum temperatures are more variable compared to minimum
temperatures in Uganda. An increasing trend in hot days, hot nights, warm nights and warm spells were also detected. At
seven of the stations, annual temperature range and diurnal temperature range trends were found to be negative. The finding
that intra-annual and intra-monthly variance is declining suggests that fewer anomalously extreme temperature episodes
occur. The gap between maximum and minimum extremes is reducing, which supports the observation that minimum
temperatures are on the increase.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0088hb201
A comparison of global marine surface specific humidity datasets from in situ observations and atmospheric reanalysis

The accurate estimation of near surface marine specific humidity is necessary for climate and air-sea interaction applications. Available estimates of monthly-mean specific humidity spanning the past 50-years are based on a variety of sources including in situ observations, atmospheric reanalyses and datasets that blend many different data sources. Eight specific humidity datasets are compared and little consensus emerges as to mean values, regional variations and changes over time. For large area averages the datasets do show consistency in their interannual variations and, in the Extratropics, in their seasonal cycles. Adjustments applied to in situ observations from ships are shown to be smaller than differences among the datasets and in well-sampled regions and periods the in situ data are able to highlight biases in the reanalysis-based specific humidity estimates. Near surface specific humidity estimates from two recent atmospheric reanalysis projects show markedly different responses in Tropical specific humidity to the assimilation of satellite radiance measurements that became available in 1999. \ud
There is less confidence in reanalysis-based estimates of specific humidity over the ocean than over land. However the in situ based humidity analyses have suffered in recent years with a reduction in observation numbers and lack of information on observation methods and heights. Consequently near-surface specific humidity remains relatively poorly known over the oceans
Year patterns of climate impacts on wheat yields

Rainfall, temperature, and solar radiation are important climate factors, which determine crop growth, development and yield from instantaneous to decadal scales. We propose to identify year patterns of climate impact on yield on the basis of rain and non-rain weather. There are inter-related impacts of climatic factors on crop production within a specific pattern. Historical wheat yield data in Queensland during 18892004 were used. The influence of meteorological conditions on wheat yields was derived from statistical yield data which were detrended by 9-year-smoothing averages to remove the effects of technological improvements on wheat yields over time. Climate affects crop growth and development differently over different growth stages. Therefore, we considered the climate effects at both vegetative and reproductive stages (before and after flowering date, respectively) on yield. Cluster analysis was employed to identify the year patterns of climate impact. Five patterns were significantly classified. Precipitation during the vegetative stage was the dominant and beneficial factor for wheat yields while increasing maximum temperature had a negative influence. Crop yields were strongly dependent on solar radiation under normal rainfall conditions
An analysis of the climate of Macaronesia, 1865-2012

New monthly, long-running, continuous surface air temperature records for four island chains throughout the Macaronesian biogeographical zone in the North Atlantic Ocean are presented. The records run from 1865 for the Azores and Madeira, 1885 for the Canary Islands and 1895 for Cape Verde. Recent (1981-2010) warming across these islands is significant in summer (JJA) for the Canary Islands, Cape Verde and Madeira, ranging from 0.40 to 0.46Â°C per decade. Annually, the temperature trends across this period range from 0.30 to 0.38Â°C per decade across all four island chains (significant for all but the Canary Islands), which exceed the station-based, average global temperature rise by up to 0.10Â°C per decade. Precipitation records from multiple islands across Macaronesia are also presented in addition to sea-level pressure records from the Azores and Cape Verde. Cape Verde wet season (ASO) precipitation is found to have significantly increased at two of our three sites from 1981 to 2010. The Azores, Canary Islands and Madeira precipitation trends display no significant changes, although the three Azores stations display a recent positive tendency. The extended Azores pressure record allows us to construct an entirely station-based Azores-Iceland North Atlantic Oscillation index (NAOI) from 1865 to 2012 and extend the daily station-based index back to 1944, further than the longest previous daily NAOI by 6 years. In addition, we use the sea-level pressure difference between the Azores and Cape Verde to create a novel method of characterizing trade wind strength across Macaronesia, the Trade Wind index (TWI), which points towards a recent, statistically significant increase (since 1973) throughout the region. Links between the winter and summer NAOI, TWI and Macaronesian temperature and precipitation are explored, as are the differences in warming trends between Macaronesia and analogous subtropical island chains, most of which are found to be warming at slower rates than the Macaronesia stations. Â© 2013 Royal Meteorological Society
Updated high-resolution grids of monthly climatic observations - the CRU TS3.10 Dataset

This paper describes the construction of an updated gridded climate dataset (referred to as CRU TS3.10) from monthly observations at meteorological stations across the world's land areas. Station anomalies (from 1961 to 1990 means) were interpolated into 0.5° latitude/longitude grid cells covering the global land surface (excluding Antarctica), and combined with an existing climatology to obtain absolute monthly values. The dataset includes six mostly independent climate variables (mean temperature, diurnal temperature range, precipitation, wet-day frequency, vapour pressure and cloud cover). Maximum and minimum temperatures have been arithmetically derived from these. Secondary variables (frost day frequency and potential evapotranspiration) have been estimated from the six primary variables using well-known formulae. Time series for hemispheric averages and 20 large sub-continental scale regions were calculated (for mean, maximum and minimum temperature and precipitation totals) and compared to a number of similar gridded products. The new dataset compares very favourably, with the major deviations mostly in regions and/or time periods with sparser observational data. CRU TS3.10 includes diagnostics associated with each interpolated value that indicates the number of stations used in the interpolation, allowing determination of the reliability of values in an objective way. This gridded product will be publicly available, including the input station series (http://www.cru.uea.ac.uk/ and http://badc.nerc.ac.uk/data/cru/)
Influence of climate change on IDF curves for the metropolitan area of Barcelona (Spain)

The evaluation of the possible climate change influence on extreme precipitation is very interesting in the Mediterranean area due to the usual and characteristic high intensities of its rainfall pattern. This analysis is also very important in urban zones, especially those densely populated with complex sewer systems, generally vulnerable to torrential rainfall. In this work, a total of 114 simulated daily rainfall series, 84 for the period 2000–2099 and 30 for the control period 1951–1999, have been analysed. These series were obtained for six thermo-pluviometric stations located in the metropolitan area of Barcelona using the information provided by five general circulation models under four future climate scenarios of greenhouse gas emissions and applying statistical downscaling methods. The potential changes in the intensity–duration–frequency relationships due to climate change have been investigated. For the last third of the 21st century, under A1B, A2 and B2 climate scenarios, an increase of at least 4% has been found on the expected daily rainfall\ud
with return period longer than 20 years. Using a temporal downscaling based on scaling properties of rainfall, future hourly\ud
extreme rainfall has been estimated. For almost all the scenarios and periods considered, the increase on the expected\ud
hourly rainfall has resulted slightly higher than the corresponding daily rainfall. The greatest differences between the future\ud
hourly and daily rainfall estimated have been found in the second third of the century under scenarios A1B (8%) and A2\ud
(9%)Postprint (published version
The role of the Sun in atmosphere-ocean coupling

Copyright © 2013 Royal Meteorological SocietyAn overview of the processes involved in determining the Sun's influence on climate is presented in the form of a flow chart. Evidence and hypotheses concerning the combined influences of the El Niño-Southern Oscillation, the Quasi-Biennial Oscillation and the Solar Cycle on the Hadley and Walker circulations are discussed in the context of atmosphere–ocean coupling, focussing on the Pacific region. It is shown that the Sun plays a crucial role in ocean–atmosphere coupling but that this coupling appears to be disturbed during the latter half of the 20th century, probably related to climate change. The identification of a solar influence can lead to improved skill in prediction so as to better inform communities to address/mitigate some of the crucial issues that are associated with climate change.Natural Environment Research Council (NERC
A new climatology for Southern Hemisphere blockings in the winter and the combined effect of ENSO and SAM phases

This study presents 53-year climatology of Southern Hemisphere (SH) blockings in the winter using\ud
daily 500-hPa geopotential height data from NCEP–NCAR reanalysis. The variability of SH blocking events and their\ud
relationships with combined phases of El Ni˜no/southern oscillation (ENSO) and the southern annular mode (SAM) are\ud
examined. Conventional indices were revised and a slightly modified index is proposed to detect latitudinal variations of\ud
SH blockings. The South Pacific region is examined in detail. There is no statistically significant long-term trend in the SH\ud
blockings. During moderate El Ni˜no, the preferred location SH blocking is observed over East Pacific, and we show that\ud
the blocking frequency increases during negative SAM phases. During moderate La Ni˜na the SH blockings are significantly\ud
suppressed over Central Pacific, with lower blocking frequency during positive SAM phases. These results indicate that\ud
the daily variability of SH blocking is strongly modulated by both ENSO and SAM phases.NOAA/OAR/ESRL PSD, Boulder, Colorado, USACAPESCNPqNOAA Office of Global Programs (NA10OAR4310170)FAPESP - 08/58101-9INCTMC/CNP
Air temperature, relative humidity, climate regionalization and thermal comfort of Nigeria

Planners and policy makers require information about the regions for which they are responsible. However, it seems that many developing countries, including Nigeria, are not adequately prepared either for their current climates or for the impact of climate change because they lack sufficient information. We have therefore examined the variations in the thermal condition in terms of the temperature, relative humidity, effective temperature (ET), temperature-humidity index (THI) and relative strain index (RSI). We studied the spatial and temporal (1951-2009, 1951-1980, 1981-2009, decadal, seasonal and monthly averages) variations in the thermal climate of Nigeria, and we divided Nigeria into thermal climate regions for effective climate change management. Mean annual minimum, mean and maximum temperatures (with their standard deviations) were 21.4 (3.5), 27.1 (2.7) and 32.8 (3.4) degrees C, respectively, while the overall mean relative humidity was 62 (24.8)%. Mean ET, THI and RSI were 24.3 (0.85), 24.8 (1.83) and 0.2 (0.18) degrees C, respectively. The ET, THI and RSI provided contrasting expressions of thermal comfort for Nigeria, because of its varied climate. We also found that elevation; the movement of the Inter Tropical Discontinuity and urbanization affect thermal comfort in Nigeria. We conclude that thermal stress has increased in Nigeria from 2000 at most stations, especially in the south and north-western regions, and that Nigerian thermal comfort climate is heterogeneous and requires analysis of multiple thermal indices