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S. Vérant, K. Laval, J. Polcher, and M. De Castro

Abstract

In the broad context of the downscaling methods that are used to study climatic change impacts, the dependence of the surface hydrological processes simulated by the Organising Carbon and Hydrology in Dynamic Ecosystem (ORCHIDEE) land surface model, used in a stand-alone mode, on the spatial scale of the forcings is investigated over the Iberian Peninsula. These prescribed forcings are the outputs of a regional climate model, Pronóstico a Mesoescala (PROMES), with a high spatial resolution (20 km). In the first experiment, the PROMES outputs have been aggregated stepwise to the typical resolution of a general circulation model, and applied to ORCHIDEE, in order to analyze the impacts of the changing resolution on the simulated water balance. Then, subgrid-scale variability (SSV) for the different forcings has been progressively reintroduced. This second experiment is aimed at isolating the crucial elements of SSV that need to be preserved when a disaggregation is being performed.

The increase of interception loss when the spatial resolution goes beyond 100 km leads to unrealistic values of the interception loss ratio. In the northern humid region, the reduction of runoff frequency when the forcings are aggregated explains the decrease in runoff production, which can reach half the high-resolution runoff. These impacts drive the adjustment of the other hydrological components. The large increase of interception loss is compensated by a reduced transpiration in a dry climate, which induces a large change in soil moisture content, and by reduced runoff in humid regions. The second experiment underlines the dominant effect of precipitation SSV, and particularly the rainfall frequency, on the correct simulation of the water balance. The significant influence of the thermodynamic variables is also analyzed.

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D. Pozo-Vázquez, M. J. Esteban-Parra, F. S. Rodrigo, and Y. Castro-Díez

Abstract

The association among ENSO, the Northern Hemisphere sea level pressure (SLP), and temperatures in Europe has been analyzed during the period 1873–1995. In the first part, the SST of the Niño-3 region has been used to select extreme cold and warm ENSO events and periods that can be regarded as normal. The study was carried out for winter with the constraints that the ENSO events were well developed during the winter of study, and that they are extreme events. Composites of winter SLP and temperatures have been made for the selected cold and warm events as well as for normal cases and compared with each other. In the North Atlantic area, no statistically significant SLP anomaly patterns were found associated with warm events, while during cold events a statistically significant anomaly pattern resembling the positive phase of the North Atlantic oscillation (NAO) was found. The temperature analysis shows statistically significant negative anomalies during cold events over the Iberian Peninsula and positive anomalies over the British Isles and southern Scandinavia, consistent with the SLP anomalies. The SLP and temperatures have also been analyzed for spring. The patterns resemble those found for winter but the anomalies have lower amplitudes. For the completion of the composite analysis, the consistency among events of the relationship between ENSO and SLP as well as between ENSO and temperatures was examined. The results show that the significant patterns found in the composite analysis in the North Atlantic area are not the result of a few major events, but rather because both the SLP and temperature anomalies in this area during cold ENSO events are stable and qualitatively similar to those found during the positive phase of the NAO. The possible physical basis for this association between NAO and ENSO is discussed.

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Leslie M. Hartten, Paul E. Johnston, Valerie M. Rodríguez Castro, and Paola S. Esteban Pérez

Abstract

Wind profiling radars are usually not calibrated with respect to reflectivity because such calibrations are both unnecessary for good wind measurements and costly. However, reflectivity from calibrated profilers can reveal many atmospheric attributes beyond winds. Establishing ways to calibrate these radars even after they have been taken out of service would expand the utility of archived profiler data. We have calibrated one operating mode of a 915-MHz profiler deployed at Manus, Papua New Guinea (1992–2001), using two methods. The first method adjusts a radar parameter until the profiler’s estimate of rainfall during stratiform events closely matches surface observations. The second adjusts the parameter so that mean brightband heights observed by the profiler (July 1992–August 1994) match the mean brightband reflectivities over the profiler as observed by the TRMM Precipitation Radar (January 1998–July 2001). The results differ by about 5% and yield very similar precipitation errors during tested stratiform events. One or both of these methods could be used on many other wind profilers, whether they have been decommissioned or are currently operational. Data from such calibrated profilers will enable research employing the equivalent reflectivity factor observed by profilers to be compared with that from other radars, and will also enable turbulent studies with C n 2.

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D. Pozo-Vázquez, S. R. Gámiz-Fortis, J. Tovar-Pescador, M. J. Esteban-Parra, and Y. Castro-DÍez

Abstract

The winter sea level pressure (SLP) anomalies in the Northern Hemisphere have been analyzed over the period 1873–2000 based on the ENSO state during the previous autumn. First, a set of extreme cold and warm ENSO events and periods that may be regarded as normal is selected using the SST data of the Niño-3 region. This selection is carried out for autumn and with the constraint that the ENSO event is well developed. For the winters following these selected autumn events, composites of Northern Hemisphere SLP anomalies have been obtained and compared to each other. A study of the consistency among events of the relationship between ENSO and SLP anomalies was also carried out. Results show the preference for a positive NAO-like SLP anomaly pattern in the North Atlantic region during the winters following autumns of strong cold ENSO events and, thus, suggest the existence of a potential source of predictability for the North Atlantic climate. An additional analysis of the winter North Atlantic Oscillation (NAO) index confirms this finding. The possible physical basis of this source of predictability for the North Atlantic climate is discussed.

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F. Domínguez-Castro, M. C. Gallego, J. M. Vaquero, R. García Herrera, M. Peña-Gallardo, A. El Kenawy, and S. M. Vicente-Serrano

Abstract

The weather diary of Felipe de Zúñiga y Ontiveros was recorded in Mexico City from 1775 to 1786. It is the earliest meteorological observational record of Mexico. The diary provides daily meteorological information for rain frequency, temperature, frost, hail, thunderstorms, and wind, with higher resolution than any other contemporary documentation or natural proxy from this region. The seasonal distributions of rainy days, temperature, hail, and thunderstorms correspond well with those from the Tacubaya Observatory in Mexico City (1886–2016). Two drought periods (1780/81 and 1785/86) and one wet period (1782/83) were identified. The drought spanning from 1785 to 1786 is known in the literature as “the hunger year” because it represented the most severe famine during the colonial period (1521–1821). This paper analyzes—for the first time—this event at a daily scale. Similar to the reported droughts of 1909/10 and 2010/11, 1785/86 was a very dry period. But the dry conditions of 1785 were followed by intense frosts that started in late August and continued through September and October. This combination led to the destruction of crops and subsequent famine. The duration of the frost does not have analogs during the instrumental period, probably because of the intense warming and land changes registered over the last years in the region.

Open access
J. A. Curry, A. Bentamy, M. A. Bourassa, D. Bourras, E. F. Bradley, M. Brunke, S. Castro, S. H. Chou, C. A. Clayson, W. J. Emery, L. Eymard, C. W. Fairall, M. Kubota, B. Lin, W. Perrie, R. A. Reeder, I. A. Renfrew, W. B. Rossow, J. Schulz, S. R. Smith, P. J. Webster, G. A. Wick, and X. Zeng

High-resolution surface fluxes over the global ocean are needed to evaluate coupled atmosphere–ocean models and weather forecasting models, provide surface forcing for ocean models, understand the regional and temporal variations of the exchange of heat between the atmosphere and ocean, and provide a large-scale context for field experiments. Under the auspices of the World Climate Research Programme (WCRP) Global Energy and Water Cycle Experiment (GEWEX) Radiation Panel, the SEAFLUX Project has been initiated to investigate producing a high-resolution satellite-based dataset of surface turbulent fluxes over the global oceans to complement the existing products for surface radiation fluxes and precipitation. The SEAFLUX Project includes the following elements: a library of in situ data, with collocated satellite data to be used in the evaluation and improvement of global flux products; organized intercomparison projects, to evaluate and improve bulk flux models and determination from the satellite of the input parameters; and coordinated evaluation of the flux products in the context of applications, such as forcing ocean models and evaluation of coupled atmosphere–ocean models. The objective of this paper is to present an overview of the status of global ocean surface flux products, the methodology being used by SEAFLUX, and the prospects for improvement of satellite-derived flux products.

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L. C. Slivinski, G. P. Compo, P. D. Sardeshmukh, J. S. Whitaker, C. McColl, R. J. Allan, P. Brohan, X. Yin, C. A. Smith, L. J. Spencer, R. S. Vose, M. Rohrer, R. P. Conroy, D. C. Schuster, J. J. Kennedy, L. Ashcroft, S. Brönnimann, M. Brunet, D. Camuffo, R. Cornes, T. A. Cram, F. Domínguez-Castro, J. E. Freeman, J. Gergis, E. Hawkins, P. D. Jones, H. Kubota, T. C. Lee, A. M. Lorrey, J. Luterbacher, C. J. Mock, R. K. Przybylak, C. Pudmenzky, V. C. Slonosky, B. Tinz, B. Trewin, X. L. Wang, C. Wilkinson, K. Wood, and P. Wyszyński

Abstract

The performance of a new historical reanalysis, the NOAA–CIRES–DOE Twentieth Century Reanalysis version 3 (20CRv3), is evaluated via comparisons with other reanalyses and independent observations. This dataset provides global, 3-hourly estimates of the atmosphere from 1806 to 2015 by assimilating only surface pressure observations and prescribing sea surface temperature, sea ice concentration, and radiative forcings. Comparisons with independent observations, other reanalyses, and satellite products suggest that 20CRv3 can reliably produce atmospheric estimates on scales ranging from weather events to long-term climatic trends. Not only does 20CRv3 recreate a “best estimate” of the weather, including extreme events, it also provides an estimate of its confidence through the use of an ensemble. Surface pressure statistics suggest that these confidence estimates are reliable. Comparisons with independent upper-air observations in the Northern Hemisphere demonstrate that 20CRv3 has skill throughout the twentieth century. Upper-air fields from 20CRv3 in the late twentieth century and early twenty-first century correlate well with full-input reanalyses, and the correlation is predicted by the confidence fields from 20CRv3. The skill of analyzed 500-hPa geopotential heights from 20CRv3 for 1979–2015 is comparable to that of modern operational 3–4-day forecasts. Finally, 20CRv3 performs well on climate time scales. Long time series and multidecadal averages of mass, circulation, and precipitation fields agree well with modern reanalyses and station- and satellite-based products. 20CRv3 is also able to capture trends in tropospheric-layer temperatures that correlate well with independent products in the twentieth century, placing recent trends in a longer historical context.

Open access
Stefan Brönnimann, Rob Allan, Linden Ashcroft, Saba Baer, Mariano Barriendos, Rudolf Brázdil, Yuri Brugnara, Manola Brunet, Michele Brunetti, Barbara Chimani, Richard Cornes, Fernando Domínguez-Castro, Janusz Filipiak, Dimitra Founda, Ricardo García Herrera, Joelle Gergis, Stefan Grab, Lisa Hannak, Heli Huhtamaa, Kim S. Jacobsen, Phil Jones, Sylvie Jourdain, Andrea Kiss, Kuanhui Elaine Lin, Andrew Lorrey, Elin Lundstad, Jürg Luterbacher, Franz Mauelshagen, Maurizio Maugeri, Nicolas Maughan, Anders Moberg, Raphael Neukom, Sharon Nicholson, Simon Noone, Øyvind Nordli, Kristín Björg Ólafsdóttir, Petra R. Pearce, Lucas Pfister, Kathleen Pribyl, Rajmund Przybylak, Christa Pudmenzky, Dubravka Rasol, Delia Reichenbach, Ladislava Řezníčková, Fernando S. Rodrigo, Christian Rohr, Oleg Skrynyk, Victoria Slonosky, Peter Thorne, Maria Antónia Valente, José M. Vaquero, Nancy E. Westcottt, Fiona Williamson, and Przemysław Wyszyński

Abstract

Instrumental meteorological measurements from periods prior to the start of national weather services are designated “early instrumental data.” They have played an important role in climate research as they allow daily to decadal variability and changes of temperature, pressure, and precipitation, including extremes, to be addressed. Early instrumental data can also help place twenty-first century climatic changes into a historical context such as defining preindustrial climate and its variability. Until recently, the focus was on long, high-quality series, while the large number of shorter series (which together also cover long periods) received little to no attention. The shift in climate and climate impact research from mean climate characteristics toward weather variability and extremes, as well as the success of historical reanalyses that make use of short series, generates a need for locating and exploring further early instrumental measurements. However, information on early instrumental series has never been electronically compiled on a global scale. Here we attempt a worldwide compilation of metadata on early instrumental meteorological records prior to 1850 (1890 for Africa and the Arctic). Our global inventory comprises information on several thousand records, about half of which have not yet been digitized (not even as monthly means), and only approximately 20% of which have made it to global repositories. The inventory will help to prioritize data rescue efforts and can be used to analyze the potential feasibility of historical weather data products. The inventory will be maintained as a living document and is a first, critical, step toward the systematic rescue and reevaluation of these highly valuable early records. Additions to the inventory are welcome.

Free access
Stefan Brönnimann, Rob Allan, Linden Ashcroft, Saba Baer, Mariano Barriendos, Rudolf Brázdil, Yuri Brugnara, Manola Brunet, Michele Brunetti, Barbara Chimani, Richard Cornes, Fernando Domínguez-Castro, Janusz Filipiak, Dimitra Founda, Ricardo García Herrera, Joelle Gergis, Stefan Grab, Lisa Hannak, Heli Huhtamaa, Kim S. Jacobsen, Phil Jones, Sylvie Jourdain, Andrea Kiss, Kuanhui Elaine Lin, Andrew Lorrey, Elin Lundstad, Jürg Luterbacher, Franz Mauelshagen, Maurizio Maugeri, Nicolas Maughan, Anders Moberg, Raphael Neukom, Sharon Nicholson, Simon Noone, Øyvind Nordli, Kristín Björg Ólafsdóttir, Petra R. Pearce, Lucas Pfister, Kathleen Pribyl, Rajmund Przybylak, Christa Pudmenzky, Dubravka Rasol, Delia Reichenbach, Ladislava Řezníčková, Fernando S. Rodrigo, Christian Rohr, Oleg Skrynyk, Victoria Slonosky, Peter Thorne, Maria Antónia Valente, José M. Vaquero, Nancy E. Westcott, Fiona Williamson, and Przemysław Wyszyński
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