[8] Stachnik, J. P., D. E. Waliser, A. J. Majda, S. N. Stechmann, and S. Thual, 2015: Evaluating MJO initiation and decay in the skeleton model using an RMM-like index. J. Geophys. Res. Atmos., 120, 11486-11508, doi:10.1002/2015JD023916. [PDF]

Fig. 6. (a, b) The first two leading modes from a multivariate EOF analysis of the 20–100 day filtered convective heating (-Ha) and zonal wind (u) model anomalies along the equator from approximately 340 years of the simulation using truncated, observed SSTs (Case-SST8N). (c, d) The first leading two modes from the observed multivariate analysis of Wheeler and Hendon (2004) showing the 15°S–15°N EOF structures of OLR and zonal wind at 850 hPa and 200 hPa (u850 and u200, respectively). The percent variance explained by each mode is shown in the top right of each panel.

Summary: This study develops a model-based MJO index that is similar to the well-known real-time multivariate MJO (RMM) index to facilitate comparison between the MJO skeleton model and observational data. Multivariate and univariate empirical orthogonal function (EOF) analyses were performed on the convective heating and zonal wind data taken from the skeleton model. The leading EOF modes indicated a wavenumber-1 convectively coupled circulation anomaly with zonal asymmetries that closely resembled the observed RMM EOFs, especially when the model was forced with observed sea surface temperatures. The overall amount of MJO activity and event lengths compared reasonably well to observations for such a simple model. The existence of slow-moving, eastward traveling waves with higher wavenumbers (k≈12) embedded within the large-scale flow often precedes MJO termination in the skeleton model.

[7] Stachnik, J. P., D. E. Waliser, and A. J. Majda, 2015: Precursor environmental conditions associated with the termination of Madden-Julian oscillation events. J. Atmos. Sci., 72, 1908-1931, doi:10.1175/JAS-D-14-0254.1. [PDF]

Fig. 4. Lead–lag composites of the 20–100-day-filtered low-level (850–700 hPa) anomalous zonal wind from reanalyses for RMM phase-2 MJO events. Composites are for (a) continuing and (b) terminal events using MERRA data. (c) The corresponding differences (terminal minus continuing) are shown. The stippling indicates the presence of a statistically significant different local mean for the continuing and terminating events using the average of a 40° window centered about the given longitude and lag. (d) Continuing, (e) terminal, and (f) difference composites for the ERA-Interim. (g)–(i) As in (d)–(f), but for CFSR data. All data are averaged from 10°S to 10°N.

Summary: A simple climatology is created using a real-time MJO monitoring index, documenting the locations and frequencies of MJO decay. Composite precursors from reanalysis indicate long-term, lower-tropospheric moisture deficits over the local domain best identifying termination events over the Indian Ocean with possible lead times as much as 20 days prior to MJO decay. Unlike the Indian Ocean and western Pacific, MJOs that terminate over the Maritime Continent appear to be related to their own intensity rather than the downstream conditions. The combination of intraseasonal vertical circulation anomalies coupled with the mean-state specific humidity best explain the anomalous moisture patterns associated with MJO termination, suggesting that the downstream influence of the MJO circulation can eventually lead to its future demise.

[6] Li, J.-L. F., W.-L. Lee, D. E. Waliser, J. P. Stachnik, E. Fetzer, S. Wong, and Q. Yue, 2014: Characterizing tropical Pacific water vapor and radiative biases in CMIP5 GCMS: Observation-based analyses and a snow and radiation interaction sensitivity experiment. J. Geophys. Res. Atmos., 119, 10981-10995, doi:10.1002/2014JD021924. [PDF]

Fig. 3. (a) The annual mean map of total precipitable water (TotWV: mm) from the NCAR CESM1 simulation with snow-radiative effect on. (b) The changes (snow-radiative effect off minus snow-radiative effect on) of annual mean maps of total precipitable water (TotWV; mm), (c) the bias of total precipitable water (mm) from the snow-radiative effect off (NoS) relative to AIRS (%), (d) same as (c) but from the simulation with snow-radiative effect on (S) relative to AIRS (%), (e) same as (c) but relative to SSM/I (%), and (f) same as (d) but relative to SSM/I (%). The simulations are CMIP5 historical runs for the twentieth century (1970–2005) using NCAR CESM1.

Summary: Significant systematic biases in the moisture fields within the tropical Pacific trade wind regions are found in the CMIP3 and CMIP5 models against profile and total column water vapor estimates from satellite observations. Positive moisture biases north of the South Pacific Convergence Zone and south of the Intertropical Convergence Zone are associated with overestimates of reflected upward shortwave, underestimates of outgoing longwave radiation at the top of atmosphere, and underestimates of downward shortwave flux at the surface. We characterize the impacts of falling snow and its radiation interaction, which are not included in most CMIP5 models, on the moisture fields using a global climate model. These findings hint at the importance of water vapor-radiation interactions in the CMIPS/CMIP5 model simulations that exclude the radiative effect of snow.

[5] Li, J.-L. F., W.-L. Lee, D. E. Waliser, J. D. Neelin, J. P. Stachnik, and T. Lee, 2014: Cloud-precipitation-radiation-dynamics interaction in global climate models: A snow and radiation interaction sensitivity experiment. J. Geophys. Res. Atmos., 119, 3809-3824, doi:10.1029/2013JD021038. [PDF]

Fig. 5. Annual mean changes (snow-radiation off minus snow-radiation on) for the zonal average (from 180°W to 120°W; 60°S to 60°N) for (a) vertical longwave (LW) heating rates (QLW; K d−1), (b) shortwave heating (QSW; K d−1), (c) net radiative heating rates (QRAD; K d−1), (d) moist diabatic heating rates (QCOND; K d−1), (e) vertical velocity (Omega; hPa h−1), (f) meridional wind (V; m s−1), and (g) zonal wind (U; m s−1).

Summary: Conventional global climate models often consider radiation interactions only with small-particle/suspended cloud mass, ignoring large-particle/falling and convective core mass. We characterize the radiation and atmospheric circulation impacts of frozen precipitating hydrometeors (i.e., snow), using the NCAR coupled GCM. The changes associated with excluding precipitating hydrometeors exhibit a number differences consistent with CMIP5 biases, including more outgoing longwave flux at the top of atmosphere and downward shortwave flux at the surface in heavily precipitating regions. Neglecting the interaction of snow develops increased instability that triggers more convection. Broader dynamical impacts include a stronger local meridional overturning circulation over the middle and east Pacific and commensurate changes in the horizontal winds and large-scale ascending motion in the tropics.

[4] Hopper, L. J., Jr., C. Schumacher, and J. P. Stachnik, 2013: Implementation and assessment of undergraduate learning experiences in SOAP: An atmospheric science research and education program. J. Geosci. Educ., 61, 415-427, doi:10.5408/12-382.1. [PDF]

Fig. 1. Total confidence scale mean response distributions (of the items that students performed each year) for first-year and multiyear SOAP participants during 2007–2010. Mann-Whitney U-test statistics, p values calculated using SPSS software, and mean ranks, item responses, and summated scores are also provided. Participants responded using a five-point Likert format (1 = no confidence, 3 = neutral, and 5 = very confident).

Summary: The Student Operational Aggie Doppler Radar Project (SOAP) involved 95 undergraduates in a research and education program to better understand the climatology of storms in southeast Texas from 2006–2010. Anonymous surveys given to SOAP students at the end of each semester indicated that student confidence in performing most SOAP tasks exhibited statistically significant positive correlations with their interest and experience in doing them. Students participating in SOAP for multiple years were significantly more confident in performing program tasks and were more likely to obtain meteorology or science-related employment upon graduation. Students were also more likely to consider research careers and graduate programs the longer they participated longer in SOAP, suggesting these programs have a strong influence on students’ career outcomes in addition to fostering positive self-efficacy.

[3] Stachnik, J. P., C. Schumacher, and P. E. Ciesielski, 2013: Total heating characteristics of the ISCCP tropical and subtropical cloud regimes. J. Climate, 26, 7097-7116, doi:10.1175/JCLI-D-12-00673.1. [PDF]

Fig. 4. Daily average total diabatic heating (Q1) composite profiles for the ISCCP cloud regimes. The ensemble average (black line) is smoothed using a 1–2–1 filter. The scale used for WS1 is different from that of the remaining panels.

Summary: Composite profiles of the apparent heat source Q1 and moisture sink Q2 are calculated for the International Satellite Cloud Climatology Project (ISCCP) cloud regimes (or ‘‘weather states’’) using sounding observations from 10 field campaigns comprising both tropical and subtropical domains. Distinct heating profiles were determined for each ISCCP cloud regime, ranging from strong, upper-tropospheric heating for mesoscale convective systems (WS1) to integrated cooling for populations typically associated with marine stratus and stratocumulus clouds (WS5, WS6, and WS7). Low-level heating anomalies were calculated for each phase of the Madden–Julian oscillation (MJO) and they precede upper-tropospheric heating from deep convection by 3–4 phases.

[2] Stachnik, J. P., and C. Schumacher, 2011: A comparison of the Hadley circulation in modern reanalyses. J. Geophys. Res., 116, D22102, doi:10.1029/2011JD016677. [PDF]

Fig. 6. Time series of the annual average (top) maximum and (bottom) minimum zonally averaged meridional mass stream function, ΨN* and ΨS*, for each reanalysis during the 1958–2008 period.

Summary: Previous studies using select reanalysis data suggest an intensification and poleward expansion of the tropical Hadley circulation (HC) throughout the twentieth century. An intercomparison of eight reanalyses is presented to better elucidate the mean state variability and trends concerning HC intensity and width. Significant variability between reanalyses was found in the mean HC intensity with less variability in HC width. Ensemble trends are broadly consistent with previous work, indicating a 0.40 (0.07) × 1010 kg s−1 decade−1 intensification in the northern (southern) cell and a 1.1° decade−1 widening in the past 30 years. Separation of the stream function magnitudes by ENSO phase revealed a weak clustering and statistically significant strengthening of the mean circulation for El Niño for the winter cell with little difference in the summer cell intensity.

[1] Lasher-Trapp, S., and J. P. Stachnik, 2007: Giant and ultragiant aerosol particle variability over the eastern Great Lakes region. J. Appl. Meteor. Climatol., 46, 651-659, doi:10.1175/JAM2490.1. [PDF]

Fig. 2. Giant aerosol (with ultragiant included, if observed) number concentration observed in clear air below 4-km altitude AGL for 14 flights during AIRS II. Data points are represented by markers. Lines connecting markers are presented only for ease in viewing different profiles, and data points below detectable limits for probe sampling volumes are not plotted.

Summary: Numerous studies have indicated the potential for giant and ultragiant aerosol particles to expedite the warm-rain process as a result of their extreme sizes. The central question regarding their importance is are they present in large enough numbers to influence the microphysics of the clouds significantly? New observations collected during the second Alliance Icing Research Study (AIRS II) document the presence and variability of these aerosol particles over a continental region, namely the eastern Great Lakes region and parts of the midwestern United States and Canada during one month in winter 2003. Sources and factors contributing to the amount of these particles observed in the lower atmosphere were difficult to identify separately; future studies incorporating high-resolution weather modeling are likely needed.