35 research outputs found

    Global Oceans

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    The Atlantic meridional overturning circulation (MOC) and heat transport (MHT) have been observed (Fig. 3.21) at several trans-basin and western boundary moored arrays (e.g., Frajka-Williams et al. 2019; Berx et al. 2021; Hummels et al. 2022), as well as by synthesizing in situ and satellite altimetry measurements at several latitudes (Hobbs and Willis 2012; Sanchez-Franks et al. 2021; Dong et al. 2021; Kersal√© et al. 2021). Here we provide updates on the MOC and MHT estimates from the Rapid Climate Change/MOC and Heatflux Array/Western Boundary Time Series (RAPID-MOCHA-WBTS) moored array at 26.5¬įN and from the synthetic approach at 41¬įN and at several latitudes in the South Atlantic. While updates for the Overturning in the Subpolar North Atlantic Program and the South Atlantic MOC Basin-wide Array at 34.5¬įS are pending, we report on recent advances in observing the variability of flows comprising the lower limb of the North Atlantic MOC, including the Meridional Overturning Variability Experiment (MOVE, 16¬įN)

    An enhanced integrated water vapour dataset from more than 10 000 global ground-based GPS stations in 2020

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    We developed a high-quality global integrated water vapour (IWV) dataset from 12‚ÄČ552 ground-based global positioning system (GPS) stations in 2020. It consists of 5‚ÄČmin GPS IWV estimates with a total number of 1‚ÄČ093‚ÄČ591‚ÄČ492 data points. The completeness rates of the IWV estimates are higher than 95‚ÄČ% at 7253 (58‚ÄČ%) stations. The dataset is an enhanced version of the existing operational GPS IWV dataset provided by the Nevada Geodetic Laboratory (NGL). The enhancement is reached by employing accurate meteorological information from the fifth generation of European ReAnalysis (ERA5) for the GPS IWV retrieval with a significantly higher spatiotemporal resolution. A dedicated data screening algorithm is also implemented. The GPS IWV dataset has a good agreement with in situ radiosonde observations at 182 collocated stations worldwide. The IWV biases are within ¬Ī3.0‚ÄČkg‚ÄČm‚ąí2 with a mean absolute bias (MAB) value of 0.69‚ÄČkg‚ÄČm‚ąí2. The standard deviations (SD) of IWV differences are no larger than 3.4‚ÄČkg‚ÄČm‚ąí2. In addition, the enhanced IWV product shows substantial improvements compared to NGL\u27s operational version, and it is thus recommended for high-accuracy applications, such as research of extreme weather events and diurnal variations of IWV and intercomparisons with other IWV retrieval techniques. Taking the radiosonde-derived IWV as reference, the MAB and SD of IWV differences are reduced by 19.5‚ÄČ% and 6.2‚ÄČ% on average, respectively. The number of unrealistic negative GPS IWV estimates is also substantially reduced by 92.4‚ÄČ% owing to the accurate zenith hydrostatic delay (ZHD) derived by ERA5. The dataset is available at https://doi.org/10.5281/zenodo.6973528 (Yuan et al., 2022)

    Global Climate

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    In 2021, both social and economic activities began to return towards the levels preceding the COVID-19 pandemic for some parts of the globe, with others still experiencing restrictions. Meanwhile, the climate has continued to respond to the ongoing increase in greenhouse gases and resulting warming. La Ni√Īa, a phenomenon which tends to depress global temperatures while changing rainfall patterns in many regions, prevailed for all but two months of the year. Despite this, 2021 was one of the six-warmest years on record as measured by global mean surface temperature with an anomaly of between +0.21¬į and +0.28¬įC above the 1991‚Äď2020 climatology. Lake surface temperatures were their highest on record during 2021. The number of warm days over land also reached a new record high. Exceptional heat waves struck the Pacific Coast of North America, leading to a new Canadian maximum temperature of 49.6¬įC at Lytton, British Columbia, on 29 June, breaking the previous national record by over 4¬įC. In Death Valley, California, the peak temperature reached 54.4¬įC on 9 July, equaling the temperature measured in 2020, and the highest temperature recorded anywhere on the globe since at least the 1930s. Over the Mediterranean, a provisional new European record of 48.8¬įC was set in Sicily on 11 August. In the atmosphere, the annual mean tropospheric temperature was among the 10 highest on record, while the stratosphere continued to cool. While La Ni√Īa was present except for June and July, likely influencing Australia‚Äôs coolest year since 2012 and wettest since 2016, other modes of variability played important roles. A negative Indian Ocean dipole event became established during July, associated with a warmer east and cooler west Indian Ocean. Northern Hemisphere winters were affected by a negative phase of the North Atlantic Oscillation at both the beginning and end of 2021. In the Southern Hemisphere, a very strong positive Southern Annular Mode (also known as the Antarctic Oscillation) contributed to New Zealand‚Äôs record warm year and to very cold temperatures over Antarctica. Land surface winds continued a slow reversal from the multi-decadal stilling, and over the ocean wind speeds were at their highest in almost a decade. La Ni√Īa conditions had a clear influence on the regional patterns of many hydrological variables. Surface specific humidity and total column water vapor over land and ocean were higher than average in almost all datasets. Relative humidity over land reached record or near-record low saturation depending on the dataset, but with mixed signals over the ocean. Satellite measurements showed that 2021 was the third cloudiest in the 19-year record. The story for precipitation was mixed, with just below-average mean precipitation falling over land and below-average mean precipitation falling over the ocean, while extreme precipitation was generally more frequent, but less intense, than average. Differences between means and extremes can be due to several factors, including using different indices, observing periods, climatological base reference periods, and levels of spatial completeness. The sharp increase in global drought area that began in mid-2019 continued in 2021, reaching a peak in August with 32% of global land area experiencing moderate or worse drought, and declining slightly thereafter. Arctic permafrost temperatures continued to rise, reaching record values at many sites, and the thickness of the layer which seasonally thaws and freezes also increased over 2020 values in a number of regions. It was the 34th-consecutive year of mass balance loss for alpine glaciers in mountainous regions, with glaciers on average 25 m thinner than in the late 1970s. And the duration of lake ice in the Northern Hemisphere was the fourth lowest in situ record dating back to 1991. The atmospheric concentrations of the major long-lived greenhouse gases, CO2, CH4, and N2O, all reached levels not seen in at least the last million years and grew at near-record rates in 2021. La Ni√Īa conditions did not appear to have any appreciable impact on their growth rates. The growth rate for CH4, of 17 ppb yr‚ąí1, was similar to that for 2020 and set yet another record, although the causes for this post-2019 acceleration are unknown presently. Overall, CO2 growth continues to dominate the increase in global radiative forcing, which increased from 3.19 to 3.23 W m‚ąí2 (watts per square meter) during the year. In 2021, stratospheric ozone did not exhibit large negative anomalies, especially near the poles, unlike 2020, where large ozone depletions appeared, mainly from dynamical effects. The positive impact of reductions in emissions of ozone depleting substances can be seen most clearly in the upper stratosphere, where such dynamical effects are less pronounced. It was the fourth-lowest fire year since global records began in 2003, though extreme regional fire activity was again seen in North America and also in Siberia; as in 2020, the effects of wildfires in these two regions led to locally large regional positive anomalies in tropospheric aerosol and carbon monoxide abundance. Vegetation is responding to the higher global mean temperatures, with the satellite-derived measures for the Northern Hemisphere for 2021 rated among the earliest starts of the growing season and the latest end of the season on record. The first bloom date for cherry trees in Kyoto, Japan, broke a 600-year record set in 1409. This year we welcome a sidebar on the global distribution of lightning, which has been recently declared an essential climate variable (ECV) by the Global Climate Observing System (GCOS). Time series and anomaly maps from many of the variables described in this chapter can be found in Plates 1.1 and 2.1. As with other chapters, many of the sections have moved from the previous 1981‚Äď2010 to the new 1991‚Äď2020 climatological reference period, in line with WMO recommendations (see Chapter 1). This is not possible for all datasets, as it is dependent on their length of record or legacy processing methods. While anomalies from the new climatology period are not so easily comparable with previous editions of this report, they more clearly highlight deviations from more recent conditions

    An enhanced integrated water vapour dataset from more than 10 000¬†global ground-based GPS stations in¬†2020

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    oai:publications.copernicus.org:essd105760We developed a high-quality global integrated water vapour¬†(IWV) dataset from 12‚ÄČ552¬†ground-based global positioning system¬†(GPS) stations in 2020. It consists of 5‚ÄČmin GPS IWV estimates with a total number of 1‚ÄČ093‚ÄČ591‚ÄČ492¬†data points. The completeness rates of the IWV estimates are higher than 95‚ÄČ% at 7253¬†(58‚ÄČ%) stations. The dataset is an enhanced version of the existing operational GPS IWV dataset provided by the Nevada Geodetic Laboratory¬†(NGL). The enhancement is reached by employing accurate meteorological information from the fifth generation of European ReAnalysis¬†(ERA5) for the GPS IWV retrieval with a significantly higher spatiotemporal resolution. A dedicated data screening algorithm is also implemented. The GPS IWV dataset has a good agreement with in situ radiosonde observations at 182 collocated stations worldwide. The IWV biases are within ¬Ī3.0‚ÄČkg‚ÄČm‚ąí2 with a mean absolute bias¬†(MAB) value of 0.69‚ÄČkg‚ÄČm‚ąí2. The standard deviations¬†(SD) of IWV differences are no larger than 3.4‚ÄČkg‚ÄČm‚ąí2. In addition, the enhanced IWV product shows substantial improvements compared to NGL's operational version, and it is thus recommended for high-accuracy applications, such as research of extreme weather events and diurnal variations of IWV and intercomparisons with other IWV retrieval techniques. Taking the radiosonde-derived IWV as reference, the MAB and SD¬†of IWV differences are reduced by 19.5‚ÄČ% and 6.2‚ÄČ% on average, respectively. The number of unrealistic negative GPS IWV estimates is also substantially reduced by 92.4‚ÄČ% owing to the accurate zenith hydrostatic delay¬†(ZHD) derived by ERA5. The dataset is available at https://doi.org/10.5281/zenodo.6973528 (Yuan et al., 2022).</p

    Global climate

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    Global Climate [in “State of the Climate in 2019"]

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    International audienceGlobal Climate is one chapter from the State of the Climate in 2019 annual report and is avail- able from https://doi.org/10.1175/BAMS-D-20-0104.1 Compiled by NOAA’s National Centers for Environmental Information, State of the Climate in 2019 is based on contributions from scien- tists from around the world. It provides a detailed update on global climate indicators, notable weather events, and other data collected by environmental monitoring stations and instru- ments located on land, water, ice, and in space.The full report is available from https://doi.org/10.1175/2020BAMSStateoftheClimate.1

    Towards a more reliable historical reanalysis: improvements for version 3 of the Twentieth Century Reanalysis system

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    Historical reanalyses that span more than a century are needed for a wide range of studies, from understanding large‚Äźscale climate trends to diagnosing the impacts of individual historical extreme weather events. The Twentieth Century Reanalysis (20CR) Project is an effort to fill this need. It is supported by the National Oceanic and Atmospheric Administration (NOAA), the Cooperative Institute for Research in Environmental Sciences (CIRES), and the U.S. Department of Energy (DOE), and is facilitated by collaboration with the international Atmospheric Circulation Reconstructions over the Earth initiative. 20CR is the first ensemble of sub‚Äźdaily global atmospheric conditions spanning over 100 years. This provides a best estimate of the weather at any given place and time as well as an estimate of its confidence and uncertainty. While extremely useful, version 2c of this dataset (20CRv2c) has several significant issues, including inaccurate estimates of confidence and a global sea level pressure bias in the mid‚Äź19th century. These and other issues can reduce its effectiveness for studies at many spatial and temporal scales. Therefore, the 20CR system underwent a series of developments to generate a significant new version of the reanalysis. The version 3 system (NOAA‚ÄźCIRES‚ÄźDOE 20CRv3) uses upgraded data assimilation methods including an adaptive inflation algorithm; has a newer, higher‚Äźresolution forecast model that specifies dry air mass; and assimilates a larger set of pressure observations. These changes have improved the ensemble‚Äźbased estimates of confidence, removed spin‚Äźup effects in the precipitation fields, and diminished the sea‚Äźlevel pressure bias. Other improvements include more accurate representations of storm intensity, smaller errors, and large‚Äźscale reductions in model bias. The 20CRv3 system is comprehensively reviewed, focusing on the aspects that have ameliorated issues in 20CRv2c. Despite the many improvements, some challenges remain, including a systematic bias in tropical precipitation and time‚Äźvarying biases in southern high‚Äźlatitude pressure fields
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