No abstract

Summary. By setting up a suitable time series model in state space form, the latest estimate of the underlying current change in a series may be computed by the Kalman ®lter. This may be done even if the observations are only available in a time-aggregated form subject to survey sampling error. A related series, possibly observed more frequently, may be used to improve the estimate of change further. The paper applies these techniques to the important problem of estimating the underlying monthly change in unemployment in the UK measured according to the de®nition of the International Labour Organisation by the Labour Force Survey. The ®tted models suggest a reduction in rootmean-squared error of around 10% over a simple estimate based on differences if a univariate model is used and a further reduction of 50% if information on claimant counts is taken into account. With seasonally unadjusted data, the bivariate model offers a gain of roughly 40% over the use of annual differences. For both adjusted and unadjusted data, there is a further gain of around 10% if the next month's ®gure on claimant counts is used. The method preferred is based on a bivariate model with unadjusted data. If the next month's claimant count is known, the root-mean-squared error for the estimate of change is just over 10 000.

The characteristics of heatwaves (HWs) in South Korea are studied using data from the European Centre for Medium-Range Weather Forecasts Reanalysis Interim (ERA Interim) dataset and from automatic surface weather stations.The synoptic conditions of three specific years (1994, 2013, and 2016) during which serious HWs affected South Korea are examined. HWs in South Korea are related to the northwestwardly extension of the western North Pacific subtropical high (WNPSH) toward the Korean Peninsula. Examination of the blocking indices revealed widespread blocking over the northern Pacific Ocean and Asia during South Korean HWs, and blocking is related to stationary weather patterns. The severe temperatures associated with HWs in this region are due to prolonged subsidence. Analysis of the moist static energy (MSE) budget indicated that the energy source of subsidence is derived from both MSE advection and the net heat flux. When compared to the synoptic situation during an HW in South Korea, the relative southward movement of the WNPSH is found before and after the HW. The blocking indices also revealed weak signals and changes in vertical motion due to MSE advection. K E Y W O R D S heatwave, maximum temperature, moist static energy budget, synoptic conditions

This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves (CCEWs), including mixed Rossby-gravity (MRG) and tropical depression-type (TD-type) waves, based on the twentieth century experiments of 18 global climate models (GCMs) from the Coupled Model Intercomparison Project phase 3 (CMIP3). The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced. The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations, indicating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened. This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation. The mean precipitation in April and May shows a double-ITCZ problem, and the horizontal resolution is important to the delayed seasonal transition of wave activity. Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone (TC) geneses, the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs, namely, a delayed and shortened TC season in the northern hemisphere.