Description of the KNMI Operational Wave Forecast Model GONO

The purpose of this report is to give a description of the GONO computercode, which is operational at KNMI for many years now. The program was developed by J.W. Sanders, and its deep water version is based on a Norwegian wave prediction model. built by C. Haug in the sixties. Shallow water effects are however important in the southern part of the North Sea. giving a limitation of the wave growth and causing important swell dissipation. A discussion of the shallow water effects. as present in GONO, is given by Sanders in Ref. 3. The computer code GONO is written in ALGOL60 and operational on the Burroughs 6700 of KNMI. The program GONO calculates wind speed. wind direction and sea energy at every grid point of the GONO grid (cf. Appendix A) and swell energy at a limited number of points only (we call these points swell points). GONO runs every six hours and it gives a 12 and 24 hours forecast as well as results based on analyzed weather maps. In the winter of '79-'80 the output of GONO was compared with measurements and the operational wave model of Bracknell (United Kingdom). (The latter GONO version differs a little bit from the version here described). The preliminary results of this comparison are given in Ref. 4. A reasonable agreement of significant wave height and low-frequency energy, as given by GONO, with the observations was found. The present version of GONO, with small modifications compared to the previous version, is operational since the end of February 1980. Essentially, the GONO model is based on two steps. First. the sea energy at every grid point is determined. To this end advection of energy is treated by means of a finite difference scheme whereas the growth of the wave energy is calculated by means of an empirical growth curve (assuming that the wave spectrum has a fixed form). The second step is the calculation of the swell. Of course, in principle swell can be treated likewise, but then one has to store swell energy (and its direction) at every time, at every grid point for every frequency band. Also. this finite difference scheme is rather crude for swell propagation. whereas. because of stability reasons. there is an upper bound for the propagation speed (in the present case the upper bound is given by 13.87 m/s). If one is only interested in swell information at particular points (swell points), it is tempting to use a ray technique. The advantage of this technique is that it is very accurate. Swell is determined in this fashion in GONO.GON

Calcium score: a new risk factor for colorectal anastomotic leakage.

Item does not contain fulltextBACKGROUND: Anastomotic leakage (AL) is the most feared complication of colorectal surgery. Atherosclerosis is suggested to have a detrimental effect on anastomotic healing. This study aimed to analyze the calcium score, a measure for atherosclerosis, as a risk factor for AL. STUDY DESIGN: The calcium scores of colorectal patients operated on in 2 Dutch university medical centers were determined using a computed tomography scan and calcium scoring software. The aorta, common iliac arteries, internal and external iliac arteries were studied. Additionally, patient- and operation-related factors were scored. RESULTS: A total of 122 patients were included. In patients with AL, calcium scores were significantly higher in the left common iliac artery (561.4 vs 156.0, P = .028), right common iliac artery (542.0 vs 144.4, P = .041), both common iliac arteries together (1,103.3 vs 301.9, P = .046), and the left internal iliac artery (716.3 vs 35.3, P = .044). CONCLUSIONS: Patients with higher calcium scores in the iliacal arteries have an increased leakage risk.01 juni 201

New climate change scenarios for the Netherlands

A new set of climate change scenarios for 2050 for the Netherlands was produced recently. The scenarios span a wide range of possible future climate conditions, and include climate variables that are of interest to a broad user community. The scenario values are constructed by combining output from an ensemble of recent General Climate Model (GCM) simulations, Regional Climate Model (RCM) output, meteorological observations and a touch of expert judgment. For temperature, precipitation, potential evaporation and wind four scenarios are constructed, encompassing ranges of both global mean temperature rise in 2050 and the strength of the response of the dominant atmospheric circulation in the area of interest to global warming. For this particular area, wintertime precipitation is seen to increase between 3.5 and 7% per degree global warming, but mean summertime precipitation shows opposite signs depending on the assumed response of the circulation regime. Annual maximum daily mean wind speed shows small changes compared to the observed (natural) variability of this variable. Sea level rise in the North Sea in 2100 ranges between 35 and 85 cm. Preliminary assessment of the impact of the new scenarios on water management and coastal defence policies indicate that particularly dry summer scenarios and increased intensity of extreme daily precipitation deserves additional attention in the near future