artificially modifying the convective and stratiform heating/cooling between 40- and 80-km radii

We describe a method for specifying the mass flux based on the convective inhibition at the top of the subcloud layer and the amount of turbulence within it.

the pressure level at which the radiative cooling decays linearly to zero is decreased from 200 to 125 mb, resulting in a ∼2.5 km increase in the depth of the cooling

shallower depth of imposed radiative cooling

Time–longitude diagram

emerge spontaneously

Equilibrium vs. activation controls

two ways, discussed above, of breaking the problem into mutually exclusiveparts: scale separation, and moist-dry separation

The convective transports are a response to this forcing,and in the main produce the opposite effect - a warming and drying. Themean atmospheric state which we observe represents some balancebetween these opposing processes. However, as one might expect, this“balanced state” shifts in the direction of the forcing. The concept of a bal-anced state while convection is in progress is closely related to the quasi-equilibrium hypothesi

Composite temperature perturbation (solid) in the vicinity of MCS-like heating(profile shown dashed) in the imposed-heating model

Large-scale upward motion in a convecting atmosphere increases convection and thus reduces the boundary-layer entropy, primarily through convective downdraughrs. Main- taining moht neutrality, the pee-atmosphere temperature is reduced. Thus the large-scale ascent ‘feels’ an effective, positive static stability

must produce disturbances in the large-scale flow, rather than producing steady vertical transports

no discontinuity in the heating

superimposed on

latent heat energy released is two orders of magnitude greater than the amount needed to maintain the kinetic energy against frictional dissipation

it may become difficult to distinguish between the ‘large-scale’ and ‘convective’ motions

conditionally unstable if it contains a nontrivial convective inhibition

statistical equilibrium was first applied systematically to the case of mist convection by Arakawa and Schubert (1974

description

time-scale of some chaotic, small-scale process is appreciably smaller than that of the large-scale

energy

small

always showed development at the smallest scales

the theory of CISK, as well as the representation of convection (Kuo 1965) that was implicitly based on it, has been an influential and lengthy dead-end road in atmospheric science

Given F(A) for all A

account for

upward motion associated with a large-scale disturbance

compromised

E is a bulk precipitation efficiency

virtually all extant simulations of convective clouds have proceeded in the ‘spin- down’ mode, in which convection is triggered by an aberration of the initial condition and thereafter uses the APE of the initial state, which is not resupplied

phase speed associated with hear normal modes

for a = 0.9

The inescapable conclusion from all these analyses is that lurge-scale ascent in convecting atmospheres is associated with a reduction of temperature; i.e. with a positive effective static stability

an equatorial Kelvin wave

The subcloud- layer entropy is reduced under the enhanced convective downdraughts associated with the ascent phase of the wave; this is, in equilibrium, associated with a reduction of the free-atmosphere temperature

very small

time-scale for clear air to subside through the troposphere, about 30 days

the conceptual simplifications inherent in statistical-equilibrium thinking will prove to be a boon to a new generation of tropical dynamicists

due to large-scale processes only

the elementary requirement that heating and temperature fluctuations must be positively correlated in order that disturbance energy be produced seems to have been overlooked here

The dominant thinking

large-scale processes onl

co-variance between temperature and vertical motion

what they characterize as a prevalent view of tropical convection

of last year

Fig. 16. Quasi-equilibrium test

Quasi-equilibrium test

intensity is assumed to be modulated by convective available potential energy (CAPE), while occurrence frequency is modulated by the ratio of convective inhibition (CIN)

the sum of the Archimedean buoyancy and the buoyancy-induced pressure gradient acceleration, because this is the actual buoyancy acceleration

convective heating in the upper and lower troposphere is the same in the control run and, thus, cannot explain the differing convective sensitivities.

By many estimates, convective entrainment is the leading source of error in global climate models

The preferred stratification established by the model convection depends on the treat-ment of precipitation and ice processes, and especially on the poorly-understood pro-cesses that determine mass flux in downdrafts associated with the evaporation ofprecipitation.

CSRM

Gravity Waves, Compensating Subsidence and Detrainment around Cumulus Clouds

At CSU, in the project's first phase, she is working with Nicholas Kedzuf, a master's student, to look at data and to establish a comprehensive inventory of ice particle properties. ("It's an absolute joy to work with such an excellent student," says Chiu.)

detailed solutions have been presented for the case of a stably stratified fluidwith a linear density gradient

Noteb y Sir Geoffrey Taylor

TheheightinmetrestowhichsmokewillrisefromvariousSOURCES IN A WIND-FREE I.C.A.N. STANDARD ATMOSPHERE

predictions made by comparing previous experimental data on unstratified fluidswith the present theory.

laboratory experiments

u (= F2/ W) vanishesvery close toxl — 2-8. This corresponds to the greatest height reached by the plumefluid. As this fluid from the plume spreads out sideways, most of it will fall back somedistance, but certainly not as far as the height corresponding with xx 2-125 atwhich the density difference first vanishes

a simpler transfer assumption was madeby Taylor (1945) in the hope that it would represent the broad outlines of themechanics of a rising plume of buoyant air without the necessity for understandingin detail how the turbulent eddies mix the heated and the ambient air

The present treatment is based on this assumption, which relates the inflow intothe edge of a convective plume to some characteristic velocity in the plume

Two governing parameters are provided by the physical conditions of theproblem, F0 and G, and these must determine the scale of the motion

Three boundary conditions are required to determine a solution

the vertical flux of buoyancy remains constant at all heights.

The conservation relations may then be written

the swapping experiment

percentage of cloudy parcels that cross the layer, which will be referred to as the crossing percentage

We binned the parcels based on their buoyancy acceleration and vertical velocity at the bottom level right before they ascend to the next level.

wind

playing

the atmosphere radiatively cools less, and this drives the 3%–4% slowdown of the tropical circulation

decompose the circulation change into a sum of relative changes in subsidence area, static stability, and heating rate.

taking advantage of the dynamical stability of these regions

Highlights

Annotation

boreal summer stationary-wave amplitude (SWA) had a significantly positive trend during 1979–2013

SWA to increasing climate forcing using 31 CMIP5 GCMs

31 CMIP5 GCMs

increased heavy-rainfall-day frequency over South Asia, the Indochinese Peninsula, and southern China (SA-EA), and to increased dry-spell-day frequency over the northwestern and central United States

models reasonably capture the temporal statistics

benchmark for model evaluation

most energetic during austral summer, facilitating interaction with the concurrent NPMM conditions

(CMIP5) are used in this study to investigate further the SPMM and its role in ENSO predictability

Pacific meridional mode, a thermodynamically coupled mode of variability, links extratropical Pacific oceanic and atmospheric anomalies to the tropical Pacific

uggestive of ocean–atmosphere coupling.

Random internal variability causes apparent decadal modulations of ENSO correlations over the Indo-western Pacific, which are high during epochs of high ENSO variance.

POGA shows skills in simulating the ENSO-forced warming of the tropical Indian Ocean and an anomalous anticyclonic circulation pattern over the northwestern tropical Pacific in the post–El Niño

El Niño–Southern Oscillation (ENSO) peaks in boreal winter but its impact on Indo-western Pacific climate persists for another two seasons

High leakage periods are also related to reduced inland convective rainfall over southeastern Africa in austral summer

we find Agulhas leakage variability to be related to a meridional shift and/or strengthening of the westerlies

recreate a number of total velocity fields by modifying the eddying component to assess the dependence of leakage variability on the eddies.

Future changes to annual frequency, LMI, and the latitude of LMI are evaluated using the downscaled tracks where large sample sizes

large-scale environmental fields

commonly applied cluster analysis: 1) explicitly simulated tracks

hypotheses

Shading from anvils causes cool anomalies in the underlying sea surface temperature (SST) of up to −0.6°C.

life cycle of mesoscale convective systems (MCS), their associated anvil clouds, and their effects on the radiation balance

from a geostationary satellite

consistent with the hypothesis that the cancellation in CRE is caused by feedbacks among cloud albedo, large-scale circulation, and SST.

investigate the accuracy of the GCM-based NCAR CAM3.0 water vapor kernel

isolate the individual cloud, atmospheric, and surface property contributions to the variability of the radiation budget

nearly zero global average of broadband RH feedback is a result of spatial compensation and spectral compensation

spectrally resolved relative humidity (RH) feedbacks for 16 GCMs that participated in CMIP5

improved winds and surface heat fluxes must go hand in hand with improved subseasonal and parameterized ocean processes. Implications

Correcting FLOR’s climatological SST and wind stress biases via flux adjustment (FA) leads to weaker deep advective cooling of the ECT, which then erodes the upper-ocean thermal stratification, enhances vertical mixing, and excessively deepens the thermocline.

about half of the model uncertainty in the midlatitude cloud–circulation coupling stems from this impact of the circulation on the large-scale temperature structure of the atmosphere, and thus could be removed by improving the climatological circulation in models.

monthly-scale advection

upper-ocean heat budget

decline in cloudiness is steeper at 1200 UTC (0800 LT), when a trend of up to −6% decade−1 is observed over the central and eastern Amazon

atmospheric rivers (ARs), narrow bands of moisture originating in the tropics.

The circulation of northward-flowing Atlantic Water at the surface and returning overflow water at depth is particularly manifested—and observed—at the Greenland–Scotland Ridge where the water masses are guided through narrow straits.

Jianping Duana,bxJianping DuanSearch for articles by this author, Lun LicxLun LiSearch for articles by this author, Zhuguo MaaxZhuguo MaSearch for articles by this author, Jan EsperdxJan EsperSearch for articles by this author, Ulf BüntgenexUlf BüntgenSearch for articles by this author, Elena XoplakifxElena XoplakiSearch for articles by this author, Dujuan ZhanggxDujuan ZhangSearch for articles by this author, Lily WanghxLily WangSearch for articles by this author, Hong YinixHong YinSearch for articles by this author, and Jürg Luterbacherf,j

Superposed epoch analysis (SEA)

empirical orthogonal function (EOF) analysis

New to v4, uncertainties are calculated for each station series

circulation patterns in the Arctic: the Arctic Oscillation (AO) and Arctic dipole (AD)

Changes in the AO and AD are relatively minor contributing factors to the projected temperature and precipitation changes in the Arctic

Relevant

The soil moisture effect, however, does not fully fit into the surface θe argument and provides additional control on monsoon rainfall by inducing regional circulation and rainfall patterns