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Nicholas R. Nalli and Richard W. Reynolds

Abstract

This paper describes daytime sea surface temperature (SST) climate analyses derived from 16 years (1985–2000) of reprocessed Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmospheres (PATMOS) multichannel radiometric data. Two satellite bias correction methods are employed: the first being an aerosol correction, the second being an in situ correction of satellite biases. The aerosol bias correction is derived from observed statistical relationships between the slant-path aerosol optical depth and AVHRR multichannel SST (MCSST) depressions for elevated levels of tropospheric and stratospheric aerosol. Weekly analyses of SST are produced on a 1° equal-angle grid using optimum interpolation (OI) methodology. Four separate OI analyses are derived based on 1) MCSST without satellite bias correction, 2) MCSST with aerosol satellite bias correction, 3) MCSST with in situ correction of satellite biases, and 4) MCSST with both aerosol and in situ corrections of satellite biases. These analyses are compared against the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager OI SST, along with the extended reconstruction SST in situ analysis product. The OI analysis 1 exhibits significant negative and positive biases. Analysis 2, derived exclusively from satellite data, reduces globally the negative bias associated with elevated atmospheric aerosol, and subsequently reveals pronounced variations in diurnal warming consistent with recently published works. Analyses 3 and 4, derived from in situ correction of satellite biases, alleviate biases (positive and negative) associated with both aerosol and diurnal warming, and also reduce the dispersion. The PATMOS OISST 1985–2000 daytime climate analyses presented here provide a high-resolution (1° weekly) empirical database for studying seasonal and interannual climate processes.

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W. J. Emery, K. Cherkauer, B. Shannon, and R. W. Reynolds

Abstract

The design and deployment of an inexpensive hull temperature sensor and data logger system was undertaken for the purpose of improving the measurement of sea surface temperature (SST) by ship-of-opportunity merchant vessels. The resulting hull sensors and data logger systems were installed on four merchant vessels and one research vessel. A variety of installations tested the effects of placement and insulation on the temperature sensors themselves. The resulting hull SST data were compared with monthly SST analyses using optimal interpolation (OI) as well as with data from the thermosalinograph (TSG) on board the research vessel. The data collected from the hull sensor systems, while being slightly offset from the TSG data (likely due to a TSG calibration problem), were found to be in excellent agreement with the monthly OI data.

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C. M. R. Platt, David W. Reynolds, and N. L. Abshire

Abstract

Radiometric data from the SMS-2 and GOES-1 geostationary satellites together with ground-based lidar scans have been combined to determine the visible albedo, infrared emittance and visible optical depth of cirrus clouds. The combined observations were made on an area of cirrus of about 10 km by 10 km square at Boulder, Colorado during two days.

A method of analysis was developed to separate out the cloud albedo from surface albedo effects, to allow for possible anisotropy in the bi-directional reflectance of solar radiation from the clouds, and to compare the data with results of theoretical calculations.

Relations between the visible albedo and the infrared emittance, which were derived from satellite data, and the visible optical depth, which was derived from lidar measurements, were compared with theoretical relations derived from two models of cloud particle scattering. The first model assumes that the cloud is composed of water (or ice) spheres and the second that it is composed of long ice cylinders. It was found that the observational data agree best with the latter model, although there are still some discrepancies.

The infrared emittances varied between 0.2 and 0.95, the corresponding albedos between 0.10 and 0.32 and the visible optical depths between 0.5 and 3.5.

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H.-M. Zhang, R. W. Reynolds, R. Lumpkin, R. Molinari, K. Arzayus, M. Johnson, and T. M. Smith

This paper describes the optimal design and its research-to-operation transition of an integrated global observing system of satellites and in situ observations. The integrated observing system is used for climate assessment using sea surface temperature (SST). Satellite observations provide superior samplings while in situ observations provide the ground truth. Observing System Simulation Experiments (OSSEs) were used to objectively design an efficient in situ system to reduce satellite biases to a required accuracy. The system design was peer reviewed and was then transitioned into operations as a U.S. contribution to the international Global Climate Observing System (GCOS). A system performance measure was also formulated and operationally tracked under the Government Performance Results Act (GPRA). Additional OSSEs assisted the planning, programming, budgeting, and execution system at the National Oceanic and Atmospheric Administration (NOAA) to maximize design efficiency. This process of research to operation and decision making enables NOAA to strategically target its observing system investments. The principles of this specific example may have potential applicability to the other components of GCOS.

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C. Donlon, I. S. Robinson, W. Wimmer, G. Fisher, M. Reynolds, R. Edwards, and T. J. Nightingale

Abstract

The infrared SST autonomous radiometer (ISAR) is a self-calibrating instrument capable of measuring in situ sea surface skin temperature (SSTskin) to an accuracy of 0.1 K. Extensive field deployments alongside two independent research radiometers measuring SSTskin using different spectral and geometric configurations show that, relatively, ISAR SSTskin has a zero bias ±0.14 K rms. The ISAR instrument has been developed for satellite SST validation and other scientific programs. The ISAR can be deployed continuously on voluntary observing ships (VOS) without any service requirement or operator intervention for periods of up to 3 months. Five ISAR instruments have been built and are in sustained use in the United States, China, and Europe. This paper describes the ISAR instrument including the special design features that enabled a single channel radiometer with a spectral bandpass of 9.6–11.5 μm to be adapted for autonomous use. The entire instrument infrared optical path is calibrated by viewing two blackbody reference cavities at different temperatures to maintain high accuracy while tolerating moderate contamination of optical components by salt deposition. During bad weather, an innovative storm shutter, triggered by a sensitive optical rain gauge, automatically seals the instrument from the external environment. Data are presented that verify the instrument calibration and functionality in such situations. A watchdog timer and auto-reboot function support automatic data logging recovery in case of power outages typically encountered on ships. An RS485 external port allows supporting instruments that are not part of the core ISAR package (e.g., a solarimeter) to be logged using the ISAR system. All data are processed by the ISAR instrument and are relayed to a host computer via the RS232 serial link as (National Electronics Manufacturers Association) NEMA-style strings allowing easy integration into many commercial onboard scientific data logging systems. In case of a communications failure, data are stored on board using a CompactFlash card that can be retrieved when the instrument is serviced. The success of the design is demonstrated using results obtained over 21 months in the English Channel and Bay of Biscay as part of a campaign to validate SSTskin observations derived from the Environmental Satellite (Envisat) Advanced Along-Track Scanning Radiometer (AATSR).

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C. K. Folland, R. W. Reynolds, M. Gordon, and D. E. Parker

Abstract

This study results from recommendations made by a 1984 WMO Expert Committee on Ocean-Atmosphere Interaction Relevant to Long-Range Forecasting. The committee suggested that comparisons be carried out between monthly sea surface temperature (SST) analyses routinely made in several different countries in near real time. Emphasis was placed on the improvement of such analyses for use in operational long-range forecasting, especially for initializing dynamical long-range forecasting models. Six different monthly averaged SST analyses have been compared. The extent to which the analyses agree on several space scales and for regions covering the global oceans is shown, together with estimates of the magnitude of various types of errors. Independent estimates of SST obtained from expendable bathythermogmphs indicate that the monthly mean Meteorological Office (UKMO), Climate Analysis Center (CAC) in situ, and CAC blended analyses showed small differences (biases) from the expendable bathythermograph data. The differences were near to or below the margins of statistical significance over the Northern Hemisphere and the Southern Hemisphere tropics. Apparent negative biases in the analyses were noted, however, in the extratropical Southern Hemisphere.

The authors finish with a discussion of recent improvements to the accuracy and scope of SST analyses for both long-range forecasting and climate studies. These improvements include an integrated analysis of ice limit, in situ and satellite SST data, and the developing use of optimum interpolation as a method of SST analysis.

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Ellen M. Sukovich, F. Martin Ralph, Faye E. Barthold, David W. Reynolds, and David R. Novak

Abstract

Extreme quantitative precipitation forecast (QPF) performance is baselined and analyzed by NOAA’s Hydrometeorology Testbed (HMT) using 11 yr of 32-km gridded QPFs from NCEP’s Weather Prediction Center (WPC). The analysis uses regional extreme precipitation thresholds, quantitatively defined as the 99th and 99.9th percentile precipitation values of all wet-site days from 2001 to 2011 for each River Forecast Center (RFC) region, to evaluate QPF performance at multiple lead times. Five verification metrics are used: probability of detection (POD), false alarm ratio (FAR), critical success index (CSI), frequency bias, and conditional mean absolute error (MAEcond). Results indicate that extreme QPFs have incrementally improved in forecast accuracy over the 11-yr period. Seasonal extreme QPFs show the highest skill during winter and the lowest skill during summer, although an increase in QPF skill is observed during September, most likely due to landfalling tropical systems. Seasonal extreme QPF skill decreases with increased lead time. Extreme QPF skill is higher over the western and northeastern RFCs and is lower over the central and southeastern RFC regions, likely due to the preponderance of convective events in the central and southeastern regions. This study extends the NOAA HMT study of regional extreme QPF performance in the western United States to include the contiguous United States and applies the regional assessment recommended therein. The method and framework applied here are readily applied to any gridded QPF dataset to define and verify extreme precipitation events.

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J. H. Mather, T. P. Ackerman, W. E. Clements, F. J. Barnes, M. D. Ivey, L. D. Hatfield, and R. M. Reynolds

The interaction of clouds and radiation is a particularly difficult issue in the study of climate change. Clouds have a large impact on the earth's radiation budget but the range of spatial and temporal scales and the complexity of the physical processes associated with clouds made these interactions difficult to simulate. The Department of Energy's Atmospheric Radiation Measurement (ARM) program was established to improve the understanding of the interaction of radiation with the atmosphere with a particular emphasis on the effects of clouds. To continue its role of providing data for the study of these interactions, the ARM program deployed an Atmospheric Radiation and Cloud Station (ARCS) in the tropical western Pacific. This site began operation in October 1996. The tropical western Pacific is a very important climatic region. It is characterized by strong solar heating, high water vapor concentrations, and active convection. The ARCS is equipped with a comprehensive suite of instruments for measuring surface radiation fluxes and properties of the atmospheric state and is intended to operate for the next 10 years. The ARCS is an integrated unit that includes a data management system, a site monitor and control system, an external communications system, redundant electrical power systems, and containers that provide shelter for the equipment as well as work space for site operators, technicians, and visiting scientists. The dataset the ARCS produces will be invaluable in studying issues related to clouds and radiation in the Tropics. The site is located in Manus Province, Papua New Guinea, at 2.060°S, 147.425°E, 300 km north of the island of New Guinea. Two more ARCS are planned for deployment across the tropical Pacific.

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E. Kalnay, M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin, M. Iredell, S. Saha, G. White, J. Woollen, Y. Zhu, M. Chelliah, W. Ebisuzaki, W. Higgins, J. Janowiak, K. C. Mo, C. Ropelewski, J. Wang, A. Leetmaa, R. Reynolds, Roy Jenne, and Dennis Joseph

The NCEP and NCAR are cooperating in a project (denoted “reanalysis”) to produce a 40-year record of global analyses of atmospheric fields in support of the needs of the research and climate monitoring communities. This effort involves the recovery of land surface, ship, rawinsonde, pibal, aircraft, satellite, and other data; quality controlling and assimilating these data with a data assimilation system that is kept unchanged over the reanalysis period 1957–96. This eliminates perceived climate jumps associated with changes in the data assimilation system.

The NCEP/NCAR 40-yr reanalysis uses a frozen state-of-the-art global data assimilation system and a database as complete as possible. The data assimilation and the model used are identical to the global system implemented operationally at the NCEP on 11 January 1995, except that the horizontal resolution is T62 (about 210 km). The database has been enhanced with many sources of observations not available in real time for operations, provided by different countries and organizations. The system has been designed with advanced quality control and monitoring components, and can produce 1 mon of reanalysis per day on a Cray YMP/8 supercomputer. Different types of output archives are being created to satisfy different user needs, including a “quick look” CD-ROM (one per year) with six tropospheric and stratospheric fields available twice daily, as well as surface, top-of-the-atmosphere, and isentropic fields. Reanalysis information and selected output is also available on-line via the Internet (http//:nic.fb4.noaa.gov:8000). A special CDROM, containing 13 years of selected observed, daily, monthly, and climatological data from the NCEP/NCAR Reanalysis, is included with this issue. Output variables are classified into four classes, depending on the degree to which they are influenced by the observations and/or the model. For example, “C” variables (such as precipitation and surface fluxes) are completely determined by the model during the data assimilation and should be used with caution. Nevertheless, a comparison of these variables with observations and with several climatologies shows that they generally contain considerable useful information. Eight-day forecasts, produced every 5 days, should be useful for predictability studies and for monitoring the quality of the observing systems.

The 40 years of reanalysis (1957–96) should be completed in early 1997. A continuation into the future through an identical Climate Data Assimilation System will allow researchers to reliably compare recent anomalies with those in earlier decades. Since changes in the observing systems will inevitably produce perceived changes in the climate, parallel reanalyses (at least 1 year long) will be generated for the periods immediately after the introduction of new observing systems, such as new types of satellite data.

NCEP plans currently call for an updated reanalysis using a state-of-the-art system every five years or so. The successive reanalyses will be greatly facilitated by the generation of the comprehensive database in the present reanalysis.

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A. B. White, M. L. Anderson, M. D. Dettinger, F. M. Ralph, A. Hinojosa, D. R. Cayan, R. K. Hartman, D. W. Reynolds, L. E. Johnson, T. L. Schneider, R. Cifelli, Z. Toth, S. I. Gutman, C. W. King, F. Gehrke, P. E. Johnston, C. Walls, D. Mann, D. J. Gottas, and T. Coleman

Abstract

During Northern Hemisphere winters, the West Coast of North America is battered by extratropical storms. The impact of these storms is of paramount concern to California, where aging water supply and flood protection infrastructures are challenged by increased standards for urban flood protection, an unusually variable weather regime, and projections of climate change. Additionally, there are inherent conflicts between releasing water to provide flood protection and storing water to meet requirements for the water supply, water quality, hydropower generation, water temperature and flow for at-risk species, and recreation. To improve reservoir management and meet the increasing demands on water, improved forecasts of precipitation, especially during extreme events, are required. Here, the authors describe how California is addressing their most important and costliest environmental issue—water management—in part, by installing a state-of-the-art observing system to better track the area’s most severe wintertime storms.

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