Papers by Paul Ciesielski
Journal of Climate, 2003
This study reports on the humidity corrections in the Tropical Ocean Global Atmosphere (TOGA) Cou... more This study reports on the humidity corrections in the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean–Atmosphere Response Experiment (COARE) upper-air sounding dataset and their impact on diagnosed properties of convection and climate over the warm pool. During COARE, sounding data were collected from 29 sites with Vaisala-manufactured systems and 13 sites with VIZ-manufactured systems. A recent publication has documented the characteristics of the humidity errors at the Vaisala sites and a procedure to correct them. This study extends that work by describing the nature of the VIZ humidity errors and their correction scheme. The corrections, which are largest in lower-tropospheric levels, generally increase the moisture in the Vaisala sondes and decrease it in the VIZ sondes. Use of the corrected humidity data gives a much different perspective on the characteristics of convection during COARE. For example, application of a simple cloud model shows that the peak in convective ...
arXiv: Atmospheric and Oceanic Physics, 2018
In order to understand the effects of cumulus convection on large-scale atmospheric motions, heat... more In order to understand the effects of cumulus convection on large-scale atmospheric motions, heat and moisture budget analyses are often performed using data from an array of radiosonde stations. Ever since the pioneering work of Yanai et al. (1973), such budgets have been based on approximate forms of moist thermodynamics. This paper presents an improved form of moist thermodynamics for such budget studies.
Following the field phase of TOGA COARE, it became evident that the sounding systems in the COARE... more Following the field phase of TOGA COARE, it became evident that the sounding systems in the COARE domain exhibited a variety of humidity errors. Vaisala RS80-H (VaH) and RS80-A (VaA) sensors used at several key sites generally reported humidities too dry. In contrast, the sounding systems around 10◦N and at several Indonesian sites used a VIZ hygristor sensor which displayed a moist bias. Because of the importance of the COARE sounding dataset to describe and understand the coupled ocean-atmospheric system in the western Pacific warm pool region, a humidity correction procedure was developed by NCAR/ATD and then applied to correct 11, 540 soundings from 42 sites. The impacts of these humidity corrected sondes are considered here.
During the North American Monsoon Experiment (NAME) an unprecedented surface data set of winds an... more During the North American Monsoon Experiment (NAME) an unprecedented surface data set of winds and thermodynamic variables was collected over the core monsoon region. The surface network included 63 automated sites with 1-30 min resolution data, 27 SMN operational sites (1-3 hourly data), and 56 US operational sites (1-3 hourly data) along the northern fringe of the monsoon region. These data, along with twice daily QuikSCAT oceanic surface winds, were quality controlled and objectively analyzed on to a uniform grid with quarter-degree, 1-h resolution for the period from 1 July - 15 August. An important application of the gridded winds is their use in diagnosing surface vertical motion due to slope flows over the Sierra Madre Occidental (SMO) terrain. With this dataset we examine the diurnal characteristics of surface fields as the monsoon evolves and compare these analyses to similar surface products from the special North American Regional Reanalysis (NARR) for NAME. Observed surface fields indicate that a robust land-sea breeze circulation is present over most of Gulf of California (GOC) region in response to the strong diurnal heating of land masses on both sides of the gulf. For reasons unclear at this time, many features of this land-sea breeze circulation are missing in the NARR. Evolution of the diurnal cycle of temperature and the land- sea breeze circulation as the monsoon progresses through the season shows a strong sensitivity to rainfall over the SMO and the coastal plains. Such a relationship likely reflects changes in land surface characteristics, such as evapotranspiration and albedo, as the forests of the SMO respond to monsoonal rains.
Two features ofYanai et al.’s profiles ofQ1 andQ2—the commonly observed double-peak structure toQ... more Two features ofYanai et al.’s profiles ofQ1 andQ2—the commonly observed double-peak structure toQ2 and an inflection in theQ1 profile below themelting level—are exploredusing estimates of convective and stratiform rainfall partitioning based on Massachusetts Institute of Technology (MIT) radar reflectivity data collected during TOGA COARE. The MIT radar data allow the Q1 and Q2 profiles to be classified according to stratiform rain fractionwithin the radar domain and,within the limitations of the datasets, allow interpretations to be made about the relative contributions of convective and stratiform precipitation to the mean profiles. The sorting of Q2 by stratiform rain fraction leads to the confirmation of previous findings that the double-peak structure in the mean profile is a result of a combination of separate contributions of convective and stratiform precipitation. The convective contribution, which has a drying peak in the lower troposphere, combines with a stratiform dryin...
Journal of Applied Meteorology and Climatology
During the Dynamics of the MJO (DYNAMO) field campaign, radiosonde launches were regularly conduc... more During the Dynamics of the MJO (DYNAMO) field campaign, radiosonde launches were regularly conducted from three small islands/atolls (Malé and Gan, Maldives, and Diego Garcia, British Indian Ocean Territory) as part of a large-scale sounding network. Comparison of island upsondes with nearby and near-contemporaneous dropsondes over the ocean provides evidence for the magnitude and scope of the islands’ influence on the surrounding atmosphere and on the island upsonde profiles. The island’s impact on the upsonde data is most prominent in the lowest 200 m. Noting that the vertical gradients of temperature, moisture, and winds over the ocean are generally constant in the lowest 0.5 km of dropsondes, a simple procedure was constructed to adjust the upsonde profiles in the lowest few hundred meters to resemble the atmospheric structures over the open ocean. This procedure was applied to the soundings from the three islands mentioned above for the October–December 2011 period of DYNAMO. A...
Journal of Geophysical Research: Atmospheres, 2021
Analyses of atmospheric heat and moisture budgets serve as an effective tool to study convective ... more Analyses of atmospheric heat and moisture budgets serve as an effective tool to study convective characteristics over a region and to provide large-scale forcing fields for various modeling applications. This paper examines two popular methods for computing large-scale atmospheric budgets: the conventional budget method (CBM) using objectively gridded analyses based primarily on radiosonde data and the constrained variational analysis (CVA) approach which supplements vertical profiles of atmospheric fields with measurements at the top of the atmosphere and at the surface to conserve mass, water, energy, and momentum. Successful budget computations are dependent on accurate sampling
and analyses of the thermodynamic state of the atmosphere and the divergence field associated with convection and the large-scale circulation that influences it. Utilizing analyses generated from data taken during Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign conducted over the central Indian Ocean from October to December 2011, we evaluate the merits of these budget approaches and examine their limitations. While many of the shortcomings of the CBM, in particular effects of sampling errors in sounding data, are effectively minimized with CVA, accurate large-scale diagnostics in CVA are dependent on reliable background fields and rainfall constraints. For the DYNAMO analyses examined, the operational model fields used as the CVA background state provided wind fields that accurately resolved the vertical structure of convection in the vicinity of Gan Island. However, biases in the model thermodynamic fields were somewhat amplified in CVA resulting in a convective environment much weaker than observed.
Journal of the Atmospheric Sciences
This study examines the westward-propagating convective disturbances with quasi-2-day intervals o... more This study examines the westward-propagating convective disturbances with quasi-2-day intervals of occurrence identified over Gan Island in the central Indian Ocean from mid- to late October 2011 during the Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign. Atmospheric sounding, satellite, and radar data are used to develop a composite of seven such disturbances. Composites and spectral analyses reveal that 1) the quasi-2-day convective events comprise westward-propagating diurnal convective disturbances with phase speeds of 10–12 m s−1 whose amplitudes are modulated on a quasi-2-day time scale on a zonal scale of ~1000 km near the longitudes of Gan; 2) the cloud life cycle of quasi-2-day convective disturbances shows a distinct pattern of tropical cloud population evolution—from shallow to deep to stratiform convection; 3) the time scales of mesoscale convective system development and boundary layer modulation play essential roles in determining the periodicity of t...
Journal of the Atmospheric Sciences
Properties of the atmospheric boundary layer (ABL) over the central Indian Ocean are investigated... more Properties of the atmospheric boundary layer (ABL) over the central Indian Ocean are investigated using sounding data obtained during the Dynamics of the MJO (DYNAMO) field campaign in 2011/12. Observations from Gan Island on Addu Atoll, the R/V Revelle, and Malé in the Maldives are used to determine the frequency of well-mixed layers and their mean thermodynamic and wind profiles. Well-mixed boundary layers or mixed layers were observed 68% of the time from the three sites, ranging from ~100-m depth in recovering convective downdraft wakes to ~925 m in undisturbed conditions, with a mean depth of 508 m. At Revelle, the site most representative of the open ocean, the ABL displayed a distinct signal of modulation by the October and November MJOs, with mixed-layer depths gradually increasing through the suppressed phases as the sea surface temperature (SST) increased leading up to the active phases, followed by frequent ABL stabilization and shallow mixed layers in recovering wakes. A...
Journal of Geophysical Research: Atmospheres
The relationships between radiation, clouds, and convection on an intraseasonal time scale are ex... more The relationships between radiation, clouds, and convection on an intraseasonal time scale are examined with data taken during the Dynamics of the Madden-Julian Oscillation (MJO) field campaign. Specifically, column-net, as well as vertical profiles of radiative heating rates, computed over Gan Island in the central Indian Ocean (IO) are used along with an objective analysis of large-scale fields to examine three MJO events that occurred during the 3 month period (October to December 2011) over this region. Longwave (LW) and shortwave radiative heating rates exhibit tilted structures, reflecting radiative effects associated with the prevalence of shallow cumulus during the dry, suppressed MJO phase followed by increasing deep convection leading into the active phase. As the convection builds going into the MJO active phase, there are increasingly top-heavy anomalous radiative heating rates while the column-net radiative cooling rate <Q r > progressively decreases. Temporal fluctuations in the cloud radiative forcing, being quite sensitive to changes in high cloudiness, are dominated by LW effects with an intraseasonal variation of~0.4-0.6 K/d. While both the water vapor and cloud fields are inextricably linked, it appears that the tilted radiative structures are more related to water vapor effects. The intraseasonal variation of column-net radiative heating <Q r > enhances the convective signal in the mean by~20% with a minimum in this enhancement 10 days prior to peak MJO rainfall and maximum~7 days after. This suggests that as MJO convective envelope weakens over the central IO, cloud-radiative feedbacks help maintain the mature MJO as it moves eastward.
ABSTRACT A major field campaign was conducted in the Indian Ocean from October 2011 through March... more ABSTRACT A major field campaign was conducted in the Indian Ocean from October 2011 through March 2012 to investigate the initiation of the Madden-Julian Oscillation (MJO). Principal partners in this experiment were Japan (CINDY2011: Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011) and the United States (DYNAMO: Dynamics of the MJO, and AMIE: ARM MJO Investigation Experiment). A primary component of the observing system was an atmospheric sounding network comprised of two sounding quadrilaterals, one north and one south of the equator over the central Indian Ocean. During the intensive observing phase of the experiment, which ended in mid-December, two prominent MJOs were observed, one in October and one in November. Over the northern sounding array (centered near 3 N) both MJOs were characterized by moistening of the low- to midtroposphere over one-to-two week periods followed by rapid midlevel drying after moderately strong low-level westerly wind bursts. Conditions over the southern array (centered near 4 S) were quite different, with less distinct modulation of the moisture field by the MJOs and more persistent convection due to the presence of a southern ITCZ. Preliminary results from moisture budget analyses indicate that during the convectively inactive phase of the MJO in the first half of October, shallow cumulus populations were prevalent over the Indian Ocean. These clouds served to moisten the lowest 2-3 km of the atmosphere and counteract the drying effects of subsidence and horizontal advection during that period. In mid-October progressively deeper convection ensued, leading up to the active phase of the MJO later in the month. However, rather than a smooth evolution of the moistening, the relative humidity field during October was characterized by a stepwise progression of the moistening in three stages, though interrupted at times by disturbances on a roughly two-day time scale. The depths of the moistened layers suggest a sequence of convection: shallow cumulus, followed by cumulus congestus, and finally deep cumulonimbus clouds. A similar progression was observed during the November, though the transition from shallow to deep convection occurred more rapidly. This pattern of convective evolution resembles that observed in TOGA COARE as well as in other studies since. It is premature to fully evaluate the moistening processes and relate them to the evolving cloud populations observed by ground-based radars in DYNAMO; however, preliminary moisture budget results are now available and will be presented at the meeting.
Monthly Weather Review, May 1, 1986
This final report includes research results from the period February, 1981 through November, 1982... more This final report includes research results from the period February, 1981 through November, 1982. Two new results combine to form the final portion of this work. They are the work by Hanna (1982) and Stevens to successfully test and demonstrate a low-order spectral climate model and the work by Ciesielski et al. (1983) to combine and test the new radiation
Journal of the Atmospheric Sciences, 2015
The Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign was conducted over the Indi... more The Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign was conducted over the Indian Ocean (IO) from October 2011 to February 2012 to investigate the initiation of the Madden–Julian oscillation (MJO). Three MJOs accompanying westerly wind events (WWEs) occurred in late October, late November, and late December 2011. Momentum budget analysis is conducted to understand the contributions of the dynamical processes involved in the wind evolution associated with the MJO over the IO during DYNAMO using European Centre for Medium-Range Weather Forecasts analysis. This analysis shows that westerly acceleration at lower levels associated with the MJO active phase generally appears to be maintained by the pressure gradient force (PGF), which could be partly canceled by meridional advection of the zonal wind. Westerly acceleration in the midtroposphere tends to be mostly attributable to vertical advection. The results herein imply that there is no simple linear dynamic model tha...
Journal of Atmospheric and Oceanic Technology, 2015
This study examines the DigiCORA and Global Climate Observing System Reference Upper-Air Network ... more This study examines the DigiCORA and Global Climate Observing System Reference Upper-Air Network (GRUAN) humidity corrections of Vaisala RS92 radiosondes at three sites over the tropical Indian Ocean and surrounding areas during the Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign in 2011. The proprietary DigiCORA correction algorithm is built into the ground station software provided by Vaisala, whereas the GRUAN correction is an open source algorithm. Included in the GRUAN data product are uncertainty estimates for their corrections. This information is used to examine the statistical consistency of the various corrections. In general, the algorithms produce a positive relative humidity (RH) correction that increases with altitude related primarily to a solar radiation dry bias adjustment. For example, in daytime soundings the relative RH correction increases from a few percent for temperatures >0°C to 20%–40% between 100 and 200 hPa. Comparison of corrected RH...
Journal of the Meteorological Society of Japan. Ser. II, 2014
During the Dynamics of the MJO (DYNAMO) field campaign in 2011, upper-air soundings were launched... more During the Dynamics of the MJO (DYNAMO) field campaign in 2011, upper-air soundings were launched in Colombo, Sri Lanka, as part of the enhanced northern sounding array (NSA) of the experiment. The Colombo soundings were affected at low levels by the diurnal heating of this large island and by flow blocking caused by elevated terrain to the east of the Colombo site. Because of the large spacing between sounding sites, these small-scale island effects are aliased onto the larger scale impacting analyses and atmospheric budgets over the DYNAMO NSA. To mitigate these local island effects on the large-scale budgets, a procedure was designed that used low-level ECMWF-analyzed fields in Sri Lanka's vicinity to estimate open-ocean conditions at Colombo's location as if the island were not present. These "unperturbed" ECMWF fields at low-levels were then merged with the observed Colombo soundings. Results indicate a beneficial impact of using these adjusted fields on several aspects of the budget analyses.
SOLA, 2009
Sounding data from the South China Sea Monsoon Experiment (SCSMEX) have provided a unique opportu... more Sounding data from the South China Sea Monsoon Experiment (SCSMEX) have provided a unique opportunity to document the variability of atmospheric mixed layers over the South China Sea (SCS) during the onset of the monsoon in this region. Six-hourly sounding data from two research vessels, deployed over the northern and southern SCS, are used to determine the mixedlayer depth and its thermodynamic properties. Results from the southern ship show the presence of mixed layers 83% of the time with a mean depth of 459 m, similar to other tropical oceanic locations. On the other hand, the northern ship exhibited mixed layers 48% of the time with a mean depth of 342 m, considerably less frequent and shallower than other tropical regions. This anomalous behavior, which was particularly evident after the monsoon onset, is likely due to northward advection of low-level warm, moist air over cooler waters, which results in very small or negative buoyancy fluxes over the northern SCS, and thus weak upward mixing of heat and moisture from the surface.
Journal of the Atmospheric Sciences, 2015
The diurnal variability and the environmental conditions that support the moisture resurgence of ... more The diurnal variability and the environmental conditions that support the moisture resurgence of MJO events observed during the Cooperative Indian Ocean Experiment on Intraseasonal Variability (CINDY)/DYNAMO campaign in October–December 2011 are investigated using in situ observations and the cloud-resolving fully air–ocean–wave Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS). Spectral density and wavelet analysis of the total precipitable water (TPW) constructed from the DYNAMO soundings and TRMM satellite precipitation reveal a deep layer of vapor resurgence during the observed Wheeler and Hendon real-time multivariate MJO index phases 5–8 (MJO suppressed phase), which include diurnal, quasi-2-, quasi-3–4-, quasi-6–8-, and quasi-16-day oscillations. A similar oscillatory pattern is found in the DYNAMO moorings sea surface temperature analysis, suggesting a tightly coupled atmosphere and ocean system during these periods. COAMPS hindcast focused on the 12–16 November ...
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Papers by Paul Ciesielski
and analyses of the thermodynamic state of the atmosphere and the divergence field associated with convection and the large-scale circulation that influences it. Utilizing analyses generated from data taken during Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign conducted over the central Indian Ocean from October to December 2011, we evaluate the merits of these budget approaches and examine their limitations. While many of the shortcomings of the CBM, in particular effects of sampling errors in sounding data, are effectively minimized with CVA, accurate large-scale diagnostics in CVA are dependent on reliable background fields and rainfall constraints. For the DYNAMO analyses examined, the operational model fields used as the CVA background state provided wind fields that accurately resolved the vertical structure of convection in the vicinity of Gan Island. However, biases in the model thermodynamic fields were somewhat amplified in CVA resulting in a convective environment much weaker than observed.
and analyses of the thermodynamic state of the atmosphere and the divergence field associated with convection and the large-scale circulation that influences it. Utilizing analyses generated from data taken during Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign conducted over the central Indian Ocean from October to December 2011, we evaluate the merits of these budget approaches and examine their limitations. While many of the shortcomings of the CBM, in particular effects of sampling errors in sounding data, are effectively minimized with CVA, accurate large-scale diagnostics in CVA are dependent on reliable background fields and rainfall constraints. For the DYNAMO analyses examined, the operational model fields used as the CVA background state provided wind fields that accurately resolved the vertical structure of convection in the vicinity of Gan Island. However, biases in the model thermodynamic fields were somewhat amplified in CVA resulting in a convective environment much weaker than observed.