Correction of Humidity Bias for Vaisala RS80-A Sondes during the AMMA 2006 Observing Period

Nuret, Mathieu; Lafore, Jean‐Philippe; Guichard, Françoise; Redelsperger, Jean‐Luc; Bock, Olivier; Agustı́-Panareda, Anna; Ngamini, Jean-Blaise

doi:10.1175/2008jtecha1103.1

Cited by 44 publications

(61 citation statements)

References 14 publications

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“…They were used to compute the bias and RMSE of the three assimilation cycles over the whole period. Even though the additional COPS soundings provide the most frequent and accurate moisture observations available, they also might have errors (Agusti-Panareda et al, 2009;Nuret et al, 2008;Bock and Nuret, 2009). However, the different comparisons carried out during COPS between RS, dropsondes, groundbased and airborne lidar data did not reveal any suspicious bias in either the RS data or the lidar data.…”

Section: Impact On the Analysesmentioning

confidence: 94%

Assimilation of water‐vapour airborne lidar observations: impact study on the COPS precipitation forecasts

Bielli

Grzeschik

Richard

et al. 2011

Quart J Royal Meteoro Soc

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The Convective and Orographically-driven Precipitation Study (COPS) carried out in summer 2007 over northeastern France and southwestern Germany provided a fairly comprehensive description of the low-troposphere water-vapour field, thanks in particular to the deployment of two airborne differential absorption lidar systems. These lidar observations were assimilated using the 3D-Var assimilation system of the Application of Research to Operations at MEsoscale (AROME) numerical weather prediction mesoscale model. The assimilation was carried out for the period 4 July-3 August by running a three-hour forward intermittent assimilation cycle. First, the impact of the lidar observations was assessed by comparing the analyses with a set of more than 200 independent soundings. The lidar observations were found to have a positive impact on the analyses by reducing the dry bias in the first 500 m above ground level and by diminishing the root-mean-square error by roughly 15% in the first km. Then the impact of the lidar observations was assessed by comparing the precipitation forecasts (obtained with and without the lidar observations for the period 15 July-2 August) with the gridded precipitation observations provided by the Vienna Enhanced Resolution Analysis. In general, the impact was found to be positive but not significant for the 24 h precipitation and positive and significant for the 6 h precipitation, with an improvement lasting up to 24 h. Some selected case studies show that the improvement was obtained through a better depiction of convection initiation or through a more accurate positioning of the precipitation systems.

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Section: Impact On the Analysesmentioning

confidence: 94%

Assimilation of water‐vapour airborne lidar observations: impact study on the COPS precipitation forecasts

Bielli

Grzeschik

Richard

et al. 2011

Quart J Royal Meteoro Soc

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“…Radiosonde data collected near each radar location (Praia (TOGA), Kawsara/Dakar (NPOL), and Niamey (MIT)) have undergone extensive quality control and corrections (Nuret et al, 2008;Agustí-Panareda et al, 2009). Sounding launch intervals were approximately 4 hours (0000, 0400, 0800, 1200, 1600, 2000 UTC) at Praia, roughly 6 hours (0000, 0600, 1200, 1800 UTC) at Niamey and Kawsara, and twice daily (0000, 1200 UTC) at Dakar.…”

Section: Radiosonde Datamentioning

confidence: 99%

Radar characteristics of continental, coastal, and maritime convection observed during AMMA/NAMMA

Guy

Rutledge

Cifelli

2011

Quart J Royal Meteoro Soc

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Ground-based radar observations at three distinct geographical locations in West Africa along a common latitudinal band (Niamey, Niger (continental), Kawsara, Senegal (coastal), and Praia, Republic of Cape Verde (maritime)) are analyzed to determine convective system characteristics in each domain during a 29-day period in 2006. Ancillary datasets provided by the African Monsoon Multidisciplinary Analyses (AMMA) and NASA-AMMA (NAMMA) field campaigns are also used to place the radar observations in context. Results show that the total precipitation is dominated by propagating mesoscale convective systems. Convective characteristics vary according to environmental properties, such as vertical shear, CAPE, and the degree of synoptic forcing. Data are bifurcated based on the presence or absence of African easterly waves. In general, African easterly waves appear to enhance mesoscale convective system strength characteristics (e.g. total precipitation and vertical reflectivity profiles) at the inland and maritime sites. The wave regime also resulted in an increased population of the largest observed mesoscale convective systems observed near the coast, which led to an increase in stratiform precipitation. Despite this increase, differentiation of convective strength characteristics was less obvious between wave and no-wave regimes at the coast. Owing to the propagating nature of these advecting mesoscale convective systems, interaction with the regional thermodynamic and dynamic environment appears to result in more variability than enhancements due to the wave regime, independent of location.

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“…Although infrared radiances are given a reduced weight in ECMWF analyses, this must be kept in mind when comparing AIRS to the model water vapour profiles. Recent comparisons with in situ measurements made by the MOZAIC commercial aircraft between 10-12 km (Luo et al, 2008) show that ECMWF could be dry biased by 10-30%, partly due to the absence of supersaturation in the model but also likely because of the 20% underestimation of water vapour in the upper troposphere by the Vaïsala RS-80 probes assimilated in the model (Nuret et. al., 2008).…”

Section: Reprobus-ecmwf Modelmentioning

confidence: 99%

Evaluation of balloon and satellite water vapour measurements in the Southern tropical and subtropical UTLS during the HIBISCUS campaign

et al. 2009

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Abstract. Balloon water vapour in situ and remote measurements in the tropical upper troposphere and lower stratosphere (UTLS) obtained during the HIBISCUS campaign around 20 • S in Brazil in February-March 2004 using a tunable diode laser (µSDLA), a surface acoustic wave (SAW) and a Vis-NIR solar occultation spectrometer (SAOZ) on a long duration balloon, have been used for evaluating the performances of satellite borne remote water vapour instruments available at the same latitude and measurement period. In the stratosphere, HALOE displays the best precision (2.5%), followed by SAGE II (7%), MIPAS (10%), and SCIAMACHY (35%), all of which show approximately constant H 2 O mixing ratios between 20-25 km. Compared to HALOE of ±10% accuracy between 0.1-100 hPa, SAGE II and SAOZ show insignificant biases, MIPAS is wetter by 10% and SCIAMACHY dryer by 20%. The currently available GOMOS profiles of 25% precision show a positive vertical gradient in error for identified reasons. Compared to these, the water vapour of the Reprobus Chemistry Transport Model, forced at pressures higher than 95 hPa by the ECMWF analyses, is dryer by about 1 ppmv (20%).In the lower stratosphere between 16-20 km, most notable features are the steep degradation of MIPAS precision below 18 km, and the appearance of biases between instruments far larger than their quoted total uncertainty. HALOE and Correspondence to: N. Montoux (nadege.montoux@latmos.ipsl.fr) SAGE II (after spectral adjustment for reducing the bias with HALOE at northern mid-latitudes) both show decreases of water vapour with a minimum at the tropopause not seen by other instruments or the model, possibly attributable to an increasing error in the HALOE altitude registration. Between 16-18 km where the water vapour concentration shows little horizontal variability, and where the µSDLA balloon measurements are not perturbed by outgassing, the average mixing ratios reported by the remote sensing instruments are substantially lower than the 4-5 ppmv observed by the µSDLA. Differences between µSDLA and HALOE and SAGE II (of the order of −2 ppmv), SCIAMACHY, MIPAS and GOMOS (−1 ppmv) and SAOZ (−0.5 ppmv), exceed the 10% uncertainty of µSDLA, implying larger systematic errors than estimated for the various instruments.In the upper troposphere, where the water vapour concentration is highly variable, AIRS v5 appears to be the most consistent within its 25% uncertainty with balloon in-situ measurements as well as ECMWF. Most of the remote measurements show less reliability in the upper troposphere, losing sensitivity possibly because of absorption line saturation in their spectral ranges (HALOE, SAGE II and SCIA-MACHY), instrument noise exceeding 100% (MIPAS) or imperfect refraction correction (GOMOS). An exception is the SAOZ-balloon, employing smaller H 2 O absorption bands in the troposphere.

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Correction of Humidity Bias for Vaisala RS80-A Sondes during the AMMA 2006 Observing Period

Cited by 44 publications

References 14 publications

Assimilation of water‐vapour airborne lidar observations: impact study on the COPS precipitation forecasts

Assimilation of water‐vapour airborne lidar observations: impact study on the COPS precipitation forecasts

Radar characteristics of continental, coastal, and maritime convection observed during AMMA/NAMMA

Evaluation of balloon and satellite water vapour measurements in the Southern tropical and subtropical UTLS during the HIBISCUS campaign

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