Porte had previously placed second overall at the opening WorldTour race of the 2016 season, the Tour Down Under in Australia in January. Porte's two podium appearances mean that he unseats previous WorldTour leader Simon Gerrans (Orica-GreenEdge), who slips to third.
Welsh Paris-Nice winner Geraint Thomas (Sky) enters the ranking in fourth spot, with Colombian Sky team-mate Sergio Henao in second.
After placing seventh overall in Paris-Nice, British rider Simon Yates (Orica-GreenEdge) makes his 2016 WorldTour ranking debut in 11th.
British outfit Team Sky takes the top spot in the team ranking, deposing the Australian-registered Orica-GreenEdge.
Thomas and Yates's positions have led to Great Britain moving up the nation ranking from seventh to third. Australia are top nation with Spain in second.
Results from the Tirreno-Adriatico stage race in Italy will be included in the ranking when the race concludes today (Monday, March 14). After that, the next counting event is Milan-San Remo on Saturday, March 19.
Watch: 2016 WorldTour contenders
WorldTour points are awarded for one-day race, tour stage and stage race overall finishing positions for counting events.
The amount of points awarded depends on the ranking of the event. For example, winning the Tour de France overall gives a rider twice as many points as winning the Eneco Tour overall.
UCI WorldTour Ranking 2016 (as at Sunday, March 13)
1. Richie Porte (Aus) BMC Racing 159 points
2. Sergio Henao (Col) Team Sky 115 points
3. Simon Gerrans (Aus) Orica-GreenEdge 112 points
4. Geraint Thomas (GBr) Team Sky 104 points
5. Alberto Contador (Spa) Tinkoff 86 points
6. Jay McCarthy (Aus) Tinkoff 68 points
7. Ilnur Zakarin (Rus) Katusha 66 points
8. Michael Woods (Can) Cannondale 54 points
9. Ion Izagirre (Spa) Movistar 51 points
10. Ruben Fernandez (Spa) Movistar 40 points
11. Simon Yates (GBr) Orica-GreenEdge 31 points
19. Ben Swift (GBr) Team Sky 8 points
1. Team Sky (Great Britain) 227 points
2. Orica-GreenEdge (Australia) 171 points
3. BMC Racing 166 points
1. Australia 367 points
2. Spain 199 points
3. Great Britain 145 points
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